trust via mark cells and save, rather than trust API request

IPython/html/services/notebooks/handlers.py

@@ -1,300 +1,288 b''
 """Tornado handlers for the notebooks web service.
 
 Authors:
 
 * Brian Granger
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import json
 
 from tornado import web
 
 from IPython.html.utils import url_path_join, url_escape
 from IPython.utils.jsonutil import date_default
 
 from IPython.html.base.handlers import (IPythonHandler, json_errors,
                                     notebook_path_regex, path_regex,
                                     notebook_name_regex)
 
 #-----------------------------------------------------------------------------
 # Notebook web service handlers
 #-----------------------------------------------------------------------------
 
 
 class NotebookHandler(IPythonHandler):
 
     SUPPORTED_METHODS = (u'GET', u'PUT', u'PATCH', u'POST', u'DELETE')
 
     def notebook_location(self, name, path=''):
         """Return the full URL location of a notebook based.
         
         Parameters
         ----------
         name : unicode
             The base name of the notebook, such as "foo.ipynb".
         path : unicode
             The URL path of the notebook.
         """
         return url_escape(url_path_join(
             self.base_url, 'api', 'notebooks', path, name
         ))
 
     def _finish_model(self, model, location=True):
         """Finish a JSON request with a model, setting relevant headers, etc."""
         if location:
             location = self.notebook_location(model['name'], model['path'])
             self.set_header('Location', location)
         self.set_header('Last-Modified', model['last_modified'])
         self.finish(json.dumps(model, default=date_default))
     
     @web.authenticated
     @json_errors
     def get(self, path='', name=None):
         """Return a Notebook or list of notebooks.
 
         * GET with path and no notebook name lists notebooks in a directory
         * GET with path and notebook name returns notebook JSON
         """
         nbm = self.notebook_manager
         # Check to see if a notebook name was given
         if name is None:
             # TODO: Remove this after we create the contents web service and directories are
             # no longer listed by the notebook web service. This should only handle notebooks
             # and not directories.
             dirs = nbm.list_dirs(path)
             notebooks = []
             index = []
             for nb in nbm.list_notebooks(path):
                 if nb['name'].lower() == 'index.ipynb':
                     index.append(nb)
                 else:
                     notebooks.append(nb)
             notebooks = index + dirs + notebooks
             self.finish(json.dumps(notebooks, default=date_default))
             return
         # get and return notebook representation
         model = nbm.get_notebook(name, path)
         self._finish_model(model, location=False)
 
     @web.authenticated
     @json_errors
     def patch(self, path='', name=None):
         """PATCH renames a notebook without re-uploading content."""
         nbm = self.notebook_manager
         if name is None:
             raise web.HTTPError(400, u'Notebook name missing')
         model = self.get_json_body()
         if model is None:
             raise web.HTTPError(400, u'JSON body missing')
         model = nbm.update_notebook(model, name, path)
         self._finish_model(model)
     
     def _copy_notebook(self, copy_from, path, copy_to=None):
         """Copy a notebook in path, optionally specifying the new name.
         
         Only support copying within the same directory.
         """
         self.log.info(u"Copying notebook from %s/%s to %s/%s",
             path, copy_from,
             path, copy_to or '',
         )
         model = self.notebook_manager.copy_notebook(copy_from, copy_to, path)
         self.set_status(201)
         self._finish_model(model)
     
     def _upload_notebook(self, model, path, name=None):
         """Upload a notebook
         
         If name specified, create it in path/name.
         """
         self.log.info(u"Uploading notebook to %s/%s", path, name or '')
         if name:
             model['name'] = name
         
         model = self.notebook_manager.create_notebook(model, path)
         self.set_status(201)
         self._finish_model(model)
     
     def _create_empty_notebook(self, path, name=None):
         """Create an empty notebook in path
         
         If name specified, create it in path/name.
         """
         self.log.info(u"Creating new notebook in %s/%s", path, name or '')
         model = {}
         if name:
             model['name'] = name
         model = self.notebook_manager.create_notebook(model, path=path)
         self.set_status(201)
         self._finish_model(model)
     
     def _save_notebook(self, model, path, name):
         """Save an existing notebook."""
         self.log.info(u"Saving notebook at %s/%s", path, name)
         model = self.notebook_manager.save_notebook(model, name, path)
         if model['path'] != path.strip('/') or model['name'] != name:
             # a rename happened, set Location header
             location = True
         else:
             location = False
         self._finish_model(model, location)
     
     @web.authenticated
     @json_errors
     def post(self, path='', name=None):
         """Create a new notebook in the specified path.
         
         POST creates new notebooks. The server always decides on the notebook name.
         
         POST /api/notebooks/path
           New untitled notebook in path. If content specified, upload a
           notebook, otherwise start empty.
         POST /api/notebooks/path?copy=OtherNotebook.ipynb
           New copy of OtherNotebook in path
         """
         
         if name is not None:
             raise web.HTTPError(400, "Only POST to directories. Use PUT for full names.")
         
         model = self.get_json_body()
         
         if model is not None:
             copy_from = model.get('copy_from')
             if copy_from:
                 if model.get('content'):
                     raise web.HTTPError(400, "Can't upload and copy at the same time.")
                 self._copy_notebook(copy_from, path)
             else:
                 self._upload_notebook(model, path)
         else:
             self._create_empty_notebook(path)
 
     @web.authenticated
     @json_errors
     def put(self, path='', name=None):
         """Saves the notebook in the location specified by name and path.
         
         PUT is very similar to POST, but the requester specifies the name,
         whereas with POST, the server picks the name.
         
         PUT /api/notebooks/path/Name.ipynb
           Save notebook at ``path/Name.ipynb``. Notebook structure is specified
           in `content` key of JSON request body. If content is not specified,
           create a new empty notebook.
         PUT /api/notebooks/path/Name.ipynb?copy=OtherNotebook.ipynb
           Copy OtherNotebook to Name
         """
         if name is None:
             raise web.HTTPError(400, "Only PUT to full names. Use POST for directories.")
         
         model = self.get_json_body()
         if model:
             copy_from = model.get('copy_from')
             if copy_from:
                 if model.get('content'):
                     raise web.HTTPError(400, "Can't upload and copy at the same time.")
                 self._copy_notebook(copy_from, path, name)
             elif self.notebook_manager.notebook_exists(name, path):
                 self._save_notebook(model, path, name)
             else:
                 self._upload_notebook(model, path, name)
         else:
             self._create_empty_notebook(path, name)
 
     @web.authenticated
     @json_errors
     def delete(self, path='', name=None):
         """delete the notebook in the given notebook path"""
         nbm = self.notebook_manager
         nbm.delete_notebook(name, path)
         self.set_status(204)
         self.finish()
 
 
-class NotebookTrustHandler(IPythonHandler):
-    
-    SUPPORTED_METHODS = ('POST')
-    
-    @web.authenticated
-    def post(self, path='', name=None):
-        """trust the specified notebook"""
-        self.notebook_manager.trust_notebook(name, path)
-        self.set_status(200)
-
-
 class NotebookCheckpointsHandler(IPythonHandler):
     
     SUPPORTED_METHODS = ('GET', 'POST')
     
     @web.authenticated
     @json_errors
     def get(self, path='', name=None):
         """get lists checkpoints for a notebook"""
         nbm = self.notebook_manager
         checkpoints = nbm.list_checkpoints(name, path)
         data = json.dumps(checkpoints, default=date_default)
         self.finish(data)
     
     @web.authenticated
     @json_errors
     def post(self, path='', name=None):
         """post creates a new checkpoint"""
         nbm = self.notebook_manager
         checkpoint = nbm.create_checkpoint(name, path)
         data = json.dumps(checkpoint, default=date_default)
         location = url_path_join(self.base_url, 'api/notebooks',
             path, name, 'checkpoints', checkpoint['id'])
         self.set_header('Location', url_escape(location))
         self.set_status(201)
         self.finish(data)
 
 
 class ModifyNotebookCheckpointsHandler(IPythonHandler):
     
     SUPPORTED_METHODS = ('POST', 'DELETE')
     
     @web.authenticated
     @json_errors
     def post(self, path, name, checkpoint_id):
         """post restores a notebook from a checkpoint"""
         nbm = self.notebook_manager
         nbm.restore_checkpoint(checkpoint_id, name, path)
         self.set_status(204)
         self.finish()
     
     @web.authenticated
     @json_errors
     def delete(self, path, name, checkpoint_id):
         """delete clears a checkpoint for a given notebook"""
         nbm = self.notebook_manager
         nbm.delete_checkpoint(checkpoint_id, name, path)
         self.set_status(204)
         self.finish()
         
 #-----------------------------------------------------------------------------
 # URL to handler mappings
 #-----------------------------------------------------------------------------
 
 
 _checkpoint_id_regex = r"(?P<checkpoint_id>[\w-]+)"
 
 default_handlers = [
-    (r"/api/notebooks%s/trust" % notebook_path_regex, NotebookTrustHandler),
     (r"/api/notebooks%s/checkpoints" % notebook_path_regex, NotebookCheckpointsHandler),
     (r"/api/notebooks%s/checkpoints/%s" % (notebook_path_regex, _checkpoint_id_regex),
         ModifyNotebookCheckpointsHandler),
     (r"/api/notebooks%s" % notebook_path_regex, NotebookHandler),
     (r"/api/notebooks%s" % path_regex, NotebookHandler),
 ]
 

IPython/html/static/notebook/js/notebook.js

@@ -1,2423 +1,2400 b''
 //----------------------------------------------------------------------------
 //  Copyright (C) 2011  The IPython Development Team
 //
 //  Distributed under the terms of the BSD License.  The full license is in
 //  the file COPYING, distributed as part of this software.
 //----------------------------------------------------------------------------
 
 //============================================================================
 // Notebook
 //============================================================================
 
 var IPython = (function (IPython) {
     "use strict";
 
     var utils = IPython.utils;
 
     /**
      * A notebook contains and manages cells.
      * 
      * @class Notebook
      * @constructor
      * @param {String} selector A jQuery selector for the notebook's DOM element
      * @param {Object} [options] A config object
      */
     var Notebook = function (selector, options) {
         this.options = options = options || {};
         this.base_url = options.base_url;
         this.notebook_path = options.notebook_path;
         this.notebook_name = options.notebook_name;
         this.element = $(selector);
         this.element.scroll();
         this.element.data("notebook", this);
         this.next_prompt_number = 1;
         this.session = null;
         this.kernel = null;
         this.clipboard = null;
         this.undelete_backup = null;
         this.undelete_index = null;
         this.undelete_below = false;
         this.paste_enabled = false;
         // It is important to start out in command mode to match the intial mode
         // of the KeyboardManager.
         this.mode = 'command';
         this.set_dirty(false);
         this.metadata = {};
         this._checkpoint_after_save = false;
         this.last_checkpoint = null;
         this.checkpoints = [];
         this.autosave_interval = 0;
         this.autosave_timer = null;
         // autosave *at most* every two minutes
         this.minimum_autosave_interval = 120000;
         // single worksheet for now
         this.worksheet_metadata = {};
         this.notebook_name_blacklist_re = /[\/\\:]/;
         this.nbformat = 3; // Increment this when changing the nbformat
         this.nbformat_minor = 0; // Increment this when changing the nbformat
         this.style();
         this.create_elements();
         this.bind_events();
     };
 
     /**
      * Tweak the notebook's CSS style.
      * 
      * @method style
      */
     Notebook.prototype.style = function () {
         $('div#notebook').addClass('border-box-sizing');
     };
 
     /**
      * Create an HTML and CSS representation of the notebook.
      * 
      * @method create_elements
      */
     Notebook.prototype.create_elements = function () {
         var that = this;
         this.element.attr('tabindex','-1');
         this.container = $("<div/>").addClass("container").attr("id", "notebook-container");
         // We add this end_space div to the end of the notebook div to:
         // i) provide a margin between the last cell and the end of the notebook
         // ii) to prevent the div from scrolling up when the last cell is being
         // edited, but is too low on the page, which browsers will do automatically.
         var end_space = $('<div/>').addClass('end_space');
         end_space.dblclick(function (e) {
             var ncells = that.ncells();
             that.insert_cell_below('code',ncells-1);
         });
         this.element.append(this.container);
         this.container.append(end_space);
     };
 
     /**
      * Bind JavaScript events: key presses and custom IPython events.
      * 
      * @method bind_events
      */
     Notebook.prototype.bind_events = function () {
         var that = this;
 
         $([IPython.events]).on('set_next_input.Notebook', function (event, data) {
             var index = that.find_cell_index(data.cell);
             var new_cell = that.insert_cell_below('code',index);
             new_cell.set_text(data.text);
             that.dirty = true;
         });
 
         $([IPython.events]).on('set_dirty.Notebook', function (event, data) {
             that.dirty = data.value;
         });
 
         $([IPython.events]).on('trust_changed.Notebook', function (event, data) {
             that.trusted = data.value;
         });
 
         $([IPython.events]).on('select.Cell', function (event, data) {
             var index = that.find_cell_index(data.cell);
             that.select(index);
         });
 
         $([IPython.events]).on('edit_mode.Cell', function (event, data) {
             that.handle_edit_mode(that.find_cell_index(data.cell));
         });
 
         $([IPython.events]).on('command_mode.Cell', function (event, data) {
             that.command_mode();
         });
 
         $([IPython.events]).on('status_autorestarting.Kernel', function () {
             IPython.dialog.modal({
                 title: "Kernel Restarting",
                 body: "The kernel appears to have died. It will restart automatically.",
                 buttons: {
                     OK : {
                         class : "btn-primary"
                     }
                 }
             });
         });
 
         var collapse_time = function (time) {
             var app_height = $('#ipython-main-app').height(); // content height
             var splitter_height = $('div#pager_splitter').outerHeight(true);
             var new_height = app_height - splitter_height;
             that.element.animate({height : new_height + 'px'}, time);
         };
 
         this.element.bind('collapse_pager', function (event, extrap) {
             var time = (extrap !== undefined) ? ((extrap.duration !== undefined ) ? extrap.duration : 'fast') : 'fast';
             collapse_time(time);
         });
 
         var expand_time = function (time) {
             var app_height = $('#ipython-main-app').height(); // content height
             var splitter_height = $('div#pager_splitter').outerHeight(true);
             var pager_height = $('div#pager').outerHeight(true);
             var new_height = app_height - pager_height - splitter_height;
             that.element.animate({height : new_height + 'px'}, time);
         };
 
         this.element.bind('expand_pager', function (event, extrap) {
             var time = (extrap !== undefined) ? ((extrap.duration !== undefined ) ? extrap.duration : 'fast') : 'fast';
             expand_time(time);
         });
         
         // Firefox 22 broke $(window).on("beforeunload")
         // I'm not sure why or how.
         window.onbeforeunload = function (e) {
             // TODO: Make killing the kernel configurable.
             var kill_kernel = false;
             if (kill_kernel) {
                 that.session.kill_kernel();
             }
             // if we are autosaving, trigger an autosave on nav-away.
             // still warn, because if we don't the autosave may fail.
             if (that.dirty) {
                 if ( that.autosave_interval ) {
                     // schedule autosave in a timeout
                     // this gives you a chance to forcefully discard changes
                     // by reloading the page if you *really* want to.
                     // the timer doesn't start until you *dismiss* the dialog.
                     setTimeout(function () {
                         if (that.dirty) {
                             that.save_notebook();
                         }
                     }, 1000);
                     return "Autosave in progress, latest changes may be lost.";
                 } else {
                     return "Unsaved changes will be lost.";
                 }
             }
             // Null is the *only* return value that will make the browser not
             // pop up the "don't leave" dialog.
             return null;
         };
     };
 
     /**
      * Set the dirty flag, and trigger the set_dirty.Notebook event
      * 
      * @method set_dirty
      */
     Notebook.prototype.set_dirty = function (value) {
         if (value === undefined) {
             value = true;
         }
         if (this.dirty == value) {
             return;
         }
         $([IPython.events]).trigger('set_dirty.Notebook', {value: value});
     };
 
     /**
      * Scroll the top of the page to a given cell.
      * 
      * @method scroll_to_cell
      * @param {Number} cell_number An index of the cell to view
      * @param {Number} time Animation time in milliseconds
      * @return {Number} Pixel offset from the top of the container
      */
     Notebook.prototype.scroll_to_cell = function (cell_number, time) {
         var cells = this.get_cells();
         time = time || 0;
         cell_number = Math.min(cells.length-1,cell_number);
         cell_number = Math.max(0             ,cell_number);
         var scroll_value = cells[cell_number].element.position().top-cells[0].element.position().top ;
         this.element.animate({scrollTop:scroll_value}, time);
         return scroll_value;
     };
 
     /**
      * Scroll to the bottom of the page.
      * 
      * @method scroll_to_bottom
      */
     Notebook.prototype.scroll_to_bottom = function () {
         this.element.animate({scrollTop:this.element.get(0).scrollHeight}, 0);
     };
 
     /**
      * Scroll to the top of the page.
      * 
      * @method scroll_to_top
      */
     Notebook.prototype.scroll_to_top = function () {
         this.element.animate({scrollTop:0}, 0);
     };
 
     // Edit Notebook metadata
 
     Notebook.prototype.edit_metadata = function () {
         var that = this;
         IPython.dialog.edit_metadata(this.metadata, function (md) {
             that.metadata = md;
         }, 'Notebook');
     };
 
     // Cell indexing, retrieval, etc.
 
     /**
      * Get all cell elements in the notebook.
      * 
      * @method get_cell_elements
      * @return {jQuery} A selector of all cell elements
      */
     Notebook.prototype.get_cell_elements = function () {
         return this.container.children("div.cell");
     };
 
     /**
      * Get a particular cell element.
      * 
      * @method get_cell_element
      * @param {Number} index An index of a cell to select
      * @return {jQuery} A selector of the given cell.
      */
     Notebook.prototype.get_cell_element = function (index) {
         var result = null;
         var e = this.get_cell_elements().eq(index);
         if (e.length !== 0) {
             result = e;
         }
         return result;
     };
 
     /**
      * Try to get a particular cell by msg_id.
      * 
      * @method get_msg_cell
      * @param {String} msg_id A message UUID
      * @return {Cell} Cell or null if no cell was found.
      */
     Notebook.prototype.get_msg_cell = function (msg_id) {
         return IPython.CodeCell.msg_cells[msg_id] || null;
     };
 
     /**
      * Count the cells in this notebook.
      * 
      * @method ncells
      * @return {Number} The number of cells in this notebook
      */
     Notebook.prototype.ncells = function () {
         return this.get_cell_elements().length;
     };
 
     /**
      * Get all Cell objects in this notebook.
      * 
      * @method get_cells
      * @return {Array} This notebook's Cell objects
      */
     // TODO: we are often calling cells as cells()[i], which we should optimize
     // to cells(i) or a new method.
     Notebook.prototype.get_cells = function () {
         return this.get_cell_elements().toArray().map(function (e) {
             return $(e).data("cell");
         });
     };
 
     /**
      * Get a Cell object from this notebook.
      * 
      * @method get_cell
      * @param {Number} index An index of a cell to retrieve
      * @return {Cell} A particular cell
      */
     Notebook.prototype.get_cell = function (index) {
         var result = null;
         var ce = this.get_cell_element(index);
         if (ce !== null) {
             result = ce.data('cell');
         }
         return result;
     };
 
     /**
      * Get the cell below a given cell.
      * 
      * @method get_next_cell
      * @param {Cell} cell The provided cell
      * @return {Cell} The next cell
      */
     Notebook.prototype.get_next_cell = function (cell) {
         var result = null;
         var index = this.find_cell_index(cell);
         if (this.is_valid_cell_index(index+1)) {
             result = this.get_cell(index+1);
         }
         return result;
     };
 
     /**
      * Get the cell above a given cell.
      * 
      * @method get_prev_cell
      * @param {Cell} cell The provided cell
      * @return {Cell} The previous cell
      */
     Notebook.prototype.get_prev_cell = function (cell) {
         // TODO: off-by-one
         // nb.get_prev_cell(nb.get_cell(1)) is null
         var result = null;
         var index = this.find_cell_index(cell);
         if (index !== null && index > 1) {
             result = this.get_cell(index-1);
         }
         return result;
     };
     
     /**
      * Get the numeric index of a given cell.
      * 
      * @method find_cell_index
      * @param {Cell} cell The provided cell
      * @return {Number} The cell's numeric index
      */
     Notebook.prototype.find_cell_index = function (cell) {
         var result = null;
         this.get_cell_elements().filter(function (index) {
             if ($(this).data("cell") === cell) {
                 result = index;
             }
         });
         return result;
     };
 
     /**
      * Get a given index , or the selected index if none is provided.
      * 
      * @method index_or_selected
      * @param {Number} index A cell's index
      * @return {Number} The given index, or selected index if none is provided.
      */
     Notebook.prototype.index_or_selected = function (index) {
         var i;
         if (index === undefined || index === null) {
             i = this.get_selected_index();
             if (i === null) {
                 i = 0;
             }
         } else {
             i = index;
         }
         return i;
     };
 
     /**
      * Get the currently selected cell.
      * @method get_selected_cell
      * @return {Cell} The selected cell
      */
     Notebook.prototype.get_selected_cell = function () {
         var index = this.get_selected_index();
         return this.get_cell(index);
     };
 
     /**
      * Check whether a cell index is valid.
      * 
      * @method is_valid_cell_index
      * @param {Number} index A cell index
      * @return True if the index is valid, false otherwise
      */
     Notebook.prototype.is_valid_cell_index = function (index) {
         if (index !== null && index >= 0 && index < this.ncells()) {
             return true;
         } else {
             return false;
         }
     };
 
     /**
      * Get the index of the currently selected cell.
      
      * @method get_selected_index
      * @return {Number} The selected cell's numeric index
      */
     Notebook.prototype.get_selected_index = function () {
         var result = null;
         this.get_cell_elements().filter(function (index) {
             if ($(this).data("cell").selected === true) {
                 result = index;
             }
         });
         return result;
     };
 
 
     // Cell selection.
 
     /**
      * Programmatically select a cell.
      * 
      * @method select
      * @param {Number} index A cell's index
      * @return {Notebook} This notebook
      */
     Notebook.prototype.select = function (index) {
         if (this.is_valid_cell_index(index)) {
             var sindex = this.get_selected_index();
             if (sindex !== null && index !== sindex) {
                 this.get_cell(sindex).unselect();
             }
             var cell = this.get_cell(index);
             cell.select();
             if (cell.cell_type === 'heading') {
                 $([IPython.events]).trigger('selected_cell_type_changed.Notebook',
                     {'cell_type':cell.cell_type,level:cell.level}
                 );
             } else {
                 $([IPython.events]).trigger('selected_cell_type_changed.Notebook',
                     {'cell_type':cell.cell_type}
                 );
             }
         }
         return this;
     };
 
     /**
      * Programmatically select the next cell.
      *
      * @method select_next
      * @return {Notebook} This notebook
      */
     Notebook.prototype.select_next = function () {
         var index = this.get_selected_index();
         this.select(index+1);
         return this;
     };
 
     /**
      * Programmatically select the previous cell.
      *
      * @method select_prev
      * @return {Notebook} This notebook
      */
     Notebook.prototype.select_prev = function () {
         var index = this.get_selected_index();
         this.select(index-1);
         return this;
     };
 
 
     // Edit/Command mode
 
     /**
      * Gets the index of the cell that is in edit mode.
      *
      * @method get_edit_index
      *
      * @return index {int}
      **/
     Notebook.prototype.get_edit_index = function () {
         var result = null;
         this.get_cell_elements().filter(function (index) {
             if ($(this).data("cell").mode === 'edit') {
                 result = index;
             }
         });
         return result;
     };
 
     /**
      * Make the notebook enter command mode.
      *
      * @method command_mode
      **/
     Notebook.prototype.command_mode = function () {
         // Make sure there isn't an edit mode cell lingering around.
         var cell = this.get_cell(this.get_edit_index());
         if (cell) {
             cell.command_mode();
         }
 
         // Notify the keyboard manager if this is a change of mode for the 
         // notebook as a whole.
         if (this.mode !== 'command') {
             this.mode = 'command';
             $([IPython.events]).trigger('command_mode.Notebook');
             IPython.keyboard_manager.command_mode();
         }
     };
 
     /**
      * Handle when a cell fires it's edit_mode event.
      *
      * @method handle_edit_mode
      * @param [index] {int} Cell index to select.  If no index is provided, 
      *  the current selected cell is used.
      **/
     Notebook.prototype.handle_edit_mode = function (index) {
         // Make sure the cell exists.
         var cell = this.get_cell(index);
         if (cell === null) { return; }
 
         // Set the cell to edit mode and notify the keyboard manager if this
         // is a change of mode for the notebook as a whole.
         if (this.mode !== 'edit') {
             cell.edit_mode();
             this.mode = 'edit';
             $([IPython.events]).trigger('edit_mode.Notebook');
             IPython.keyboard_manager.edit_mode();
         }
     };
 
     /**
      * Make a cell enter edit mode.
      *
      * @method edit_mode
      * @param [index] {int} Cell index to select.  If no index is provided, 
      *  the current selected cell is used.
      **/
     Notebook.prototype.edit_mode = function (index) {
         if (index===undefined) {
             index = this.get_selected_index();
         }
         // Make sure the cell exists.
         var cell = this.get_cell(index);
         if (cell === null) { return; }
         if (cell.mode != 'edit') {
             cell.unrender();
             cell.focus_editor();
         }
     };
 
     /**
      * Focus the currently selected cell.
      *
      * @method focus_cell
      **/
     Notebook.prototype.focus_cell = function () {
         var cell = this.get_selected_cell();
         if (cell === null) {return;}  // No cell is selected
         cell.focus_cell();
     };
 
     // Cell movement
 
     /**
      * Move given (or selected) cell up and select it.
      * 
      * @method move_cell_up
      * @param [index] {integer} cell index
      * @return {Notebook} This notebook
      **/
     Notebook.prototype.move_cell_up = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i) && i > 0) {
             var pivot = this.get_cell_element(i-1);
             var tomove = this.get_cell_element(i);
             if (pivot !== null && tomove !== null) {
                 tomove.detach();
                 pivot.before(tomove);
                 this.select(i-1);
                 var cell = this.get_selected_cell();
                 cell.focus_cell();
             }
             this.set_dirty(true);
         }
         return this;
     };
 
 
     /**
      * Move given (or selected) cell down and select it
      * 
      * @method move_cell_down
      * @param [index] {integer} cell index
      * @return {Notebook} This notebook
      **/
     Notebook.prototype.move_cell_down = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i) && this.is_valid_cell_index(i+1)) {
             var pivot = this.get_cell_element(i+1);
             var tomove = this.get_cell_element(i);
             if (pivot !== null && tomove !== null) {
                 tomove.detach();
                 pivot.after(tomove);
                 this.select(i+1);
                 var cell = this.get_selected_cell();
                 cell.focus_cell();
             }
         }
         this.set_dirty();
         return this;
     };
 
 
     // Insertion, deletion.
 
     /**
      * Delete a cell from the notebook.
      * 
      * @method delete_cell
      * @param [index] A cell's numeric index
      * @return {Notebook} This notebook
      */
     Notebook.prototype.delete_cell = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_selected_cell();
         this.undelete_backup = cell.toJSON();
         $('#undelete_cell').removeClass('disabled');
         if (this.is_valid_cell_index(i)) {
             var old_ncells = this.ncells();
             var ce = this.get_cell_element(i);
             ce.remove();
             if (i === 0) {
                 // Always make sure we have at least one cell.
                 if (old_ncells === 1) {
                     this.insert_cell_below('code');
                 }
                 this.select(0);
                 this.undelete_index = 0;
                 this.undelete_below = false;
             } else if (i === old_ncells-1 && i !== 0) {
                 this.select(i-1);
                 this.undelete_index = i - 1;
                 this.undelete_below = true;
             } else {
                 this.select(i);
                 this.undelete_index = i;
                 this.undelete_below = false;
             }
             $([IPython.events]).trigger('delete.Cell', {'cell': cell, 'index': i});
             this.set_dirty(true);
         }
         return this;
     };
 
     /**
      * Restore the most recently deleted cell.
      * 
      * @method undelete
      */
     Notebook.prototype.undelete_cell = function() {
         if (this.undelete_backup !== null && this.undelete_index !== null) {
             var current_index = this.get_selected_index();
             if (this.undelete_index < current_index) {
                 current_index = current_index + 1;
             }
             if (this.undelete_index >= this.ncells()) {
                 this.select(this.ncells() - 1);
             }
             else {
                 this.select(this.undelete_index);
             }
             var cell_data = this.undelete_backup;
             var new_cell = null;
             if (this.undelete_below) {
                 new_cell = this.insert_cell_below(cell_data.cell_type);
             } else {
                 new_cell = this.insert_cell_above(cell_data.cell_type);
             }
             new_cell.fromJSON(cell_data);
             if (this.undelete_below) {
                 this.select(current_index+1);
             } else {
                 this.select(current_index);
             }
             this.undelete_backup = null;
             this.undelete_index = null;
         }
         $('#undelete_cell').addClass('disabled');
     };
 
     /**
      * Insert a cell so that after insertion the cell is at given index.
      *
      * Similar to insert_above, but index parameter is mandatory
      *
      * Index will be brought back into the accissible range [0,n]
      *
      * @method insert_cell_at_index
      * @param type {string} in ['code','markdown','heading']
      * @param [index] {int} a valid index where to inser cell
      *
      * @return cell {cell|null} created cell or null
      **/
     Notebook.prototype.insert_cell_at_index = function(type, index){
 
         var ncells = this.ncells();
         index = Math.min(index,ncells);
         index = Math.max(index,0);
         var cell = null;
 
         if (ncells === 0 || this.is_valid_cell_index(index) || index === ncells) {
             if (type === 'code') {
                 cell = new IPython.CodeCell(this.kernel);
                 cell.set_input_prompt();
             } else if (type === 'markdown') {
                 cell = new IPython.MarkdownCell();
             } else if (type === 'raw') {
                 cell = new IPython.RawCell();
             } else if (type === 'heading') {
                 cell = new IPython.HeadingCell();
             }
 
             if(this._insert_element_at_index(cell.element,index)) {
                 cell.render();
                 $([IPython.events]).trigger('create.Cell', {'cell': cell, 'index': index});
                 cell.refresh();
                 // We used to select the cell after we refresh it, but there
                 // are now cases were this method is called where select is
                 // not appropriate. The selection logic should be handled by the
                 // caller of the the top level insert_cell methods.
                 this.set_dirty(true);
             }
         }
         return cell;
 
     };
 
     /**
      * Insert an element at given cell index.
      *
      * @method _insert_element_at_index
      * @param element {dom element} a cell element
      * @param [index] {int} a valid index where to inser cell
      * @private
      *
      * return true if everything whent fine.
      **/
     Notebook.prototype._insert_element_at_index = function(element, index){
         if (element === undefined){
             return false;
         }
 
         var ncells = this.ncells();
 
         if (ncells === 0) {
             // special case append if empty
             this.element.find('div.end_space').before(element);
         } else if ( ncells === index ) {
             // special case append it the end, but not empty
             this.get_cell_element(index-1).after(element);
         } else if (this.is_valid_cell_index(index)) {
             // otherwise always somewhere to append to
             this.get_cell_element(index).before(element);
         } else {
             return false;
         }
 
         if (this.undelete_index !== null && index <= this.undelete_index) {
             this.undelete_index = this.undelete_index + 1;
             this.set_dirty(true);
         }
         return true;
     };
 
     /**
      * Insert a cell of given type above given index, or at top
      * of notebook if index smaller than 0.
      *
      * default index value is the one of currently selected cell
      *
      * @method insert_cell_above
      * @param type {string} cell type
      * @param [index] {integer}
      *
      * @return handle to created cell or null
      **/
     Notebook.prototype.insert_cell_above = function (type, index) {
         index = this.index_or_selected(index);
         return this.insert_cell_at_index(type, index);
     };
 
     /**
      * Insert a cell of given type below given index, or at bottom
      * of notebook if index greater thatn number of cell
      *
      * default index value is the one of currently selected cell
      *
      * @method insert_cell_below
      * @param type {string} cell type
      * @param [index] {integer}
      *
      * @return handle to created cell or null
      *
      **/
     Notebook.prototype.insert_cell_below = function (type, index) {
         index = this.index_or_selected(index);
         return this.insert_cell_at_index(type, index+1);
     };
 
 
     /**
      * Insert cell at end of notebook
      *
      * @method insert_cell_at_bottom
      * @param {String} type cell type
      *
      * @return the added cell; or null
      **/
     Notebook.prototype.insert_cell_at_bottom = function (type){
         var len = this.ncells();
         return this.insert_cell_below(type,len-1);
     };
 
     /**
      * Turn a cell into a code cell.
      * 
      * @method to_code
      * @param {Number} [index] A cell's index
      */
     Notebook.prototype.to_code = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i)) {
             var source_element = this.get_cell_element(i);
             var source_cell = source_element.data("cell");
             if (!(source_cell instanceof IPython.CodeCell)) {
                 var target_cell = this.insert_cell_below('code',i);
                 var text = source_cell.get_text();
                 if (text === source_cell.placeholder) {
                     text = '';
                 }
                 target_cell.set_text(text);
                 // make this value the starting point, so that we can only undo
                 // to this state, instead of a blank cell
                 target_cell.code_mirror.clearHistory();
                 source_element.remove();
                 this.select(i);
                 this.set_dirty(true);
             }
         }
     };
 
     /**
      * Turn a cell into a Markdown cell.
      * 
      * @method to_markdown
      * @param {Number} [index] A cell's index
      */
     Notebook.prototype.to_markdown = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i)) {
             var source_element = this.get_cell_element(i);
             var source_cell = source_element.data("cell");
             if (!(source_cell instanceof IPython.MarkdownCell)) {
                 var target_cell = this.insert_cell_below('markdown',i);
                 var text = source_cell.get_text();
                 if (text === source_cell.placeholder) {
                     text = '';
                 }
                 // We must show the editor before setting its contents
                 target_cell.unrender();
                 target_cell.set_text(text);
                 // make this value the starting point, so that we can only undo
                 // to this state, instead of a blank cell
                 target_cell.code_mirror.clearHistory();
                 source_element.remove();
                 this.select(i);
                 if ((source_cell instanceof IPython.TextCell) && source_cell.rendered) {
                     target_cell.render();
                 }
                 this.set_dirty(true);
             }
         }
     };
 
     /**
      * Turn a cell into a raw text cell.
      * 
      * @method to_raw
      * @param {Number} [index] A cell's index
      */
     Notebook.prototype.to_raw = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i)) {
             var source_element = this.get_cell_element(i);
             var source_cell = source_element.data("cell");
             var target_cell = null;
             if (!(source_cell instanceof IPython.RawCell)) {
                 target_cell = this.insert_cell_below('raw',i);
                 var text = source_cell.get_text();
                 if (text === source_cell.placeholder) {
                     text = '';
                 }
                 // We must show the editor before setting its contents
                 target_cell.unrender();
                 target_cell.set_text(text);
                 // make this value the starting point, so that we can only undo
                 // to this state, instead of a blank cell
                 target_cell.code_mirror.clearHistory();
                 source_element.remove();
                 this.select(i);
                 this.set_dirty(true);
             }
         }
     };
 
     /**
      * Turn a cell into a heading cell.
      * 
      * @method to_heading
      * @param {Number} [index] A cell's index
      * @param {Number} [level] A heading level (e.g., 1 becomes &lt;h1&gt;)
      */
     Notebook.prototype.to_heading = function (index, level) {
         level = level || 1;
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i)) {
             var source_element = this.get_cell_element(i);
             var source_cell = source_element.data("cell");
             var target_cell = null;
             if (source_cell instanceof IPython.HeadingCell) {
                 source_cell.set_level(level);
             } else {
                 target_cell = this.insert_cell_below('heading',i);
                 var text = source_cell.get_text();
                 if (text === source_cell.placeholder) {
                     text = '';
                 }
                 // We must show the editor before setting its contents
                 target_cell.set_level(level);
                 target_cell.unrender();
                 target_cell.set_text(text);
                 // make this value the starting point, so that we can only undo
                 // to this state, instead of a blank cell
                 target_cell.code_mirror.clearHistory();
                 source_element.remove();
                 this.select(i);
                 if ((source_cell instanceof IPython.TextCell) && source_cell.rendered) {
                     target_cell.render();
                 }
             }
             this.set_dirty(true);
             $([IPython.events]).trigger('selected_cell_type_changed.Notebook',
                 {'cell_type':'heading',level:level}
             );
         }
     };
 
 
     // Cut/Copy/Paste
 
     /**
      * Enable UI elements for pasting cells.
      * 
      * @method enable_paste
      */
     Notebook.prototype.enable_paste = function () {
         var that = this;
         if (!this.paste_enabled) {
             $('#paste_cell_replace').removeClass('disabled')
                 .on('click', function () {that.paste_cell_replace();});
             $('#paste_cell_above').removeClass('disabled')
                 .on('click', function () {that.paste_cell_above();});
             $('#paste_cell_below').removeClass('disabled')
                 .on('click', function () {that.paste_cell_below();});
             this.paste_enabled = true;
         }
     };
 
     /**
      * Disable UI elements for pasting cells.
      * 
      * @method disable_paste
      */
     Notebook.prototype.disable_paste = function () {
         if (this.paste_enabled) {
             $('#paste_cell_replace').addClass('disabled').off('click');
             $('#paste_cell_above').addClass('disabled').off('click');
             $('#paste_cell_below').addClass('disabled').off('click');
             this.paste_enabled = false;
         }
     };
 
     /**
      * Cut a cell.
      * 
      * @method cut_cell
      */
     Notebook.prototype.cut_cell = function () {
         this.copy_cell();
         this.delete_cell();
     };
 
     /**
      * Copy a cell.
      * 
      * @method copy_cell
      */
     Notebook.prototype.copy_cell = function () {
         var cell = this.get_selected_cell();
         this.clipboard = cell.toJSON();
         this.enable_paste();
     };
 
     /**
      * Replace the selected cell with a cell in the clipboard.
      * 
      * @method paste_cell_replace
      */
     Notebook.prototype.paste_cell_replace = function () {
         if (this.clipboard !== null && this.paste_enabled) {
             var cell_data = this.clipboard;
             var new_cell = this.insert_cell_above(cell_data.cell_type);
             new_cell.fromJSON(cell_data);
             var old_cell = this.get_next_cell(new_cell);
             this.delete_cell(this.find_cell_index(old_cell));
             this.select(this.find_cell_index(new_cell));
         }
     };
 
     /**
      * Paste a cell from the clipboard above the selected cell.
      * 
      * @method paste_cell_above
      */
     Notebook.prototype.paste_cell_above = function () {
         if (this.clipboard !== null && this.paste_enabled) {
             var cell_data = this.clipboard;
             var new_cell = this.insert_cell_above(cell_data.cell_type);
             new_cell.fromJSON(cell_data);
             new_cell.focus_cell();
         }
     };
 
     /**
      * Paste a cell from the clipboard below the selected cell.
      * 
      * @method paste_cell_below
      */
     Notebook.prototype.paste_cell_below = function () {
         if (this.clipboard !== null && this.paste_enabled) {
             var cell_data = this.clipboard;
             var new_cell = this.insert_cell_below(cell_data.cell_type);
             new_cell.fromJSON(cell_data);
             new_cell.focus_cell();
         }
     };
 
     // Split/merge
 
     /**
      * Split the selected cell into two, at the cursor.
      * 
      * @method split_cell
      */
     Notebook.prototype.split_cell = function () {
         var mdc = IPython.MarkdownCell;
         var rc = IPython.RawCell;
         var cell = this.get_selected_cell();
         if (cell.is_splittable()) {
             var texta = cell.get_pre_cursor();
             var textb = cell.get_post_cursor();
             if (cell instanceof IPython.CodeCell) {
                 // In this case the operations keep the notebook in its existing mode
                 // so we don't need to do any post-op mode changes.
                 cell.set_text(textb);
                 var new_cell = this.insert_cell_above('code');
                 new_cell.set_text(texta);
             } else if ((cell instanceof mdc && !cell.rendered) || (cell instanceof rc)) {
                 // We know cell is !rendered so we can use set_text.
                 cell.set_text(textb);
                 var new_cell = this.insert_cell_above(cell.cell_type);
                 // Unrender the new cell so we can call set_text.
                 new_cell.unrender();
                 new_cell.set_text(texta);
             }
         }
     };
 
     /**
      * Combine the selected cell into the cell above it.
      * 
      * @method merge_cell_above
      */
     Notebook.prototype.merge_cell_above = function () {
         var mdc = IPython.MarkdownCell;
         var rc = IPython.RawCell;
         var index = this.get_selected_index();
         var cell = this.get_cell(index);
         var render = cell.rendered;
         if (!cell.is_mergeable()) {
             return;
         }
         if (index > 0) {
             var upper_cell = this.get_cell(index-1);
             if (!upper_cell.is_mergeable()) {
                 return;
             }
             var upper_text = upper_cell.get_text();
             var text = cell.get_text();
             if (cell instanceof IPython.CodeCell) {
                 cell.set_text(upper_text+'\n'+text);
             } else if ((cell instanceof mdc) || (cell instanceof rc)) {
                 cell.unrender(); // Must unrender before we set_text.
                 cell.set_text(upper_text+'\n\n'+text);
                 if (render) {
                     // The rendered state of the final cell should match
                     // that of the original selected cell;
                     cell.render();
                 }
             }
             this.delete_cell(index-1);
             this.select(this.find_cell_index(cell));
         }
     };
 
     /**
      * Combine the selected cell into the cell below it.
      * 
      * @method merge_cell_below
      */
     Notebook.prototype.merge_cell_below = function () {
         var mdc = IPython.MarkdownCell;
         var rc = IPython.RawCell;
         var index = this.get_selected_index();
         var cell = this.get_cell(index);
         var render = cell.rendered;
         if (!cell.is_mergeable()) {
             return;
         }
         if (index < this.ncells()-1) {
             var lower_cell = this.get_cell(index+1);
             if (!lower_cell.is_mergeable()) {
                 return;
             }
             var lower_text = lower_cell.get_text();
             var text = cell.get_text();
             if (cell instanceof IPython.CodeCell) {
                 cell.set_text(text+'\n'+lower_text);
             } else if ((cell instanceof mdc) || (cell instanceof rc)) {
                 cell.unrender(); // Must unrender before we set_text.
                 cell.set_text(text+'\n\n'+lower_text);
                 if (render) {
                     // The rendered state of the final cell should match
                     // that of the original selected cell;
                     cell.render();
                 }
             }
             this.delete_cell(index+1);
             this.select(this.find_cell_index(cell));
         }
     };
 
 
     // Cell collapsing and output clearing
 
     /**
      * Hide a cell's output.
      * 
      * @method collapse_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.collapse_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof IPython.CodeCell)) {
             cell.collapse_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Hide each code cell's output area.
      * 
      * @method collapse_all_output
      */
     Notebook.prototype.collapse_all_output = function () {
         $.map(this.get_cells(), function (cell, i) {
             if (cell instanceof IPython.CodeCell) {
                 cell.collapse_output();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     /**
      * Show a cell's output.
      * 
      * @method expand_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.expand_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof IPython.CodeCell)) {
             cell.expand_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Expand each code cell's output area, and remove scrollbars.
      * 
      * @method expand_all_output
      */
     Notebook.prototype.expand_all_output = function () {
         $.map(this.get_cells(), function (cell, i) {
             if (cell instanceof IPython.CodeCell) {
                 cell.expand_output();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     /**
      * Clear the selected CodeCell's output area.
      * 
      * @method clear_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.clear_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof IPython.CodeCell)) {
             cell.clear_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Clear each code cell's output area.
      * 
      * @method clear_all_output
      */
     Notebook.prototype.clear_all_output = function () {
         $.map(this.get_cells(), function (cell, i) {
             if (cell instanceof IPython.CodeCell) {
                 cell.clear_output();
             }
         });
         this.set_dirty(true);
     };
 
     /**
      * Scroll the selected CodeCell's output area.
      * 
      * @method scroll_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.scroll_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof IPython.CodeCell)) {
             cell.scroll_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Expand each code cell's output area, and add a scrollbar for long output.
      * 
      * @method scroll_all_output
      */
     Notebook.prototype.scroll_all_output = function () {
         $.map(this.get_cells(), function (cell, i) {
             if (cell instanceof IPython.CodeCell) {
                 cell.scroll_output();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     /** Toggle whether a cell's output is collapsed or expanded.
      * 
      * @method toggle_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.toggle_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof IPython.CodeCell)) {
             cell.toggle_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Hide/show the output of all cells.
      * 
      * @method toggle_all_output
      */
     Notebook.prototype.toggle_all_output = function () {
         $.map(this.get_cells(), function (cell, i) {
             if (cell instanceof IPython.CodeCell) {
                 cell.toggle_output();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     /**
      * Toggle a scrollbar for long cell outputs.
      * 
      * @method toggle_output_scroll
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.toggle_output_scroll = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof IPython.CodeCell)) {
             cell.toggle_output_scroll();
             this.set_dirty(true);
         }
     };
 
     /**
      * Toggle the scrolling of long output on all cells.
      * 
      * @method toggle_all_output_scrolling
      */
     Notebook.prototype.toggle_all_output_scroll = function () {
         $.map(this.get_cells(), function (cell, i) {
             if (cell instanceof IPython.CodeCell) {
                 cell.toggle_output_scroll();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     // Other cell functions: line numbers, ...
 
     /**
      * Toggle line numbers in the selected cell's input area.
      * 
      * @method cell_toggle_line_numbers
      */
     Notebook.prototype.cell_toggle_line_numbers = function() {
         this.get_selected_cell().toggle_line_numbers();
     };
 
     // Session related things
 
     /**
      * Start a new session and set it on each code cell.
      * 
      * @method start_session
      */
     Notebook.prototype.start_session = function () {
         this.session = new IPython.Session(this, this.options);
         this.session.start($.proxy(this._session_started, this));
     };
 
 
     /**
      * Once a session is started, link the code cells to the kernel and pass the 
      * comm manager to the widget manager
      *
      */
     Notebook.prototype._session_started = function(){
         this.kernel = this.session.kernel;
         var ncells = this.ncells();
         for (var i=0; i<ncells; i++) {
             var cell = this.get_cell(i);
             if (cell instanceof IPython.CodeCell) {
                 cell.set_kernel(this.session.kernel);
             }
         }
     };
     
     /**
      * Prompt the user to restart the IPython kernel.
      * 
      * @method restart_kernel
      */
     Notebook.prototype.restart_kernel = function () {
         var that = this;
         IPython.dialog.modal({
             title : "Restart kernel or continue running?",
             body : $("<p/>").text(
                 'Do you want to restart the current kernel?  You will lose all variables defined in it.'
             ),
             buttons : {
                 "Continue running" : {},
                 "Restart" : {
                     "class" : "btn-danger",
                     "click" : function() {
                         that.session.restart_kernel();
                     }
                 }
             }
         });
     };
     
     /**
      * Execute or render cell outputs and go into command mode.
      * 
      * @method execute_cell
      */
     Notebook.prototype.execute_cell = function () {
         // mode = shift, ctrl, alt
         var cell = this.get_selected_cell();
         var cell_index = this.find_cell_index(cell);
         
         cell.execute();
         cell.focus_cell();
         this.command_mode();
         this.set_dirty(true);
     };
 
     /**
      * Execute or render cell outputs and insert a new cell below.
      * 
      * @method execute_cell_and_insert_below
      */
     Notebook.prototype.execute_cell_and_insert_below = function () {
         var cell = this.get_selected_cell();
         var cell_index = this.find_cell_index(cell);
         
         cell.execute();
 
         // If we are at the end always insert a new cell and return
         if (cell_index === (this.ncells()-1)) {
             this.insert_cell_below('code');
             this.edit_mode(cell_index+1);
             this.scroll_to_bottom();
             this.set_dirty(true);
             return;
         }
   
         this.insert_cell_below('code');
         this.edit_mode(cell_index+1);
         this.set_dirty(true);
     };
 
     /**
      * Execute or render cell outputs and select the next cell.
      * 
      * @method execute_cell_and_select_below
      */
     Notebook.prototype.execute_cell_and_select_below = function () {
 
         var cell = this.get_selected_cell();
         var cell_index = this.find_cell_index(cell);
         
         cell.execute();
 
         // If we are at the end always insert a new cell and return
         if (cell_index === (this.ncells()-1)) {
             this.insert_cell_below('code');
             this.edit_mode(cell_index+1);
             this.scroll_to_bottom();
             this.set_dirty(true);
             return;
         }
 
         this.select(cell_index+1);
         this.get_cell(cell_index+1).focus_cell();
         this.command_mode();
         this.set_dirty(true);
     };
 
     /**
      * Execute all cells below the selected cell.
      * 
      * @method execute_cells_below
      */
     Notebook.prototype.execute_cells_below = function () {
         this.execute_cell_range(this.get_selected_index(), this.ncells());
         this.scroll_to_bottom();
     };
 
     /**
      * Execute all cells above the selected cell.
      * 
      * @method execute_cells_above
      */
     Notebook.prototype.execute_cells_above = function () {
         this.execute_cell_range(0, this.get_selected_index());
     };
 
     /**
      * Execute all cells.
      * 
      * @method execute_all_cells
      */
     Notebook.prototype.execute_all_cells = function () {
         this.execute_cell_range(0, this.ncells());
         this.scroll_to_bottom();
     };
 
     /**
      * Execute a contiguous range of cells.
      * 
      * @method execute_cell_range
      * @param {Number} start Index of the first cell to execute (inclusive)
      * @param {Number} end Index of the last cell to execute (exclusive)
      */
     Notebook.prototype.execute_cell_range = function (start, end) {
         for (var i=start; i<end; i++) {
             this.select(i);
             this.execute_cell();
         }
     };
 
     // Persistance and loading
 
     /**
      * Getter method for this notebook's name.
      * 
      * @method get_notebook_name
      * @return {String} This notebook's name (excluding file extension)
      */
     Notebook.prototype.get_notebook_name = function () {
         var nbname = this.notebook_name.substring(0,this.notebook_name.length-6);
         return nbname;
     };
 
     /**
      * Setter method for this notebook's name.
      *
      * @method set_notebook_name
      * @param {String} name A new name for this notebook
      */
     Notebook.prototype.set_notebook_name = function (name) {
         this.notebook_name = name;
     };
 
     /**
      * Check that a notebook's name is valid.
      * 
      * @method test_notebook_name
      * @param {String} nbname A name for this notebook
      * @return {Boolean} True if the name is valid, false if invalid
      */
     Notebook.prototype.test_notebook_name = function (nbname) {
         nbname = nbname || '';
         if (nbname.length>0 && !this.notebook_name_blacklist_re.test(nbname)) {
             return true;
         } else {
             return false;
         }
     };
 
     /**
      * Load a notebook from JSON (.ipynb).
      * 
      * This currently handles one worksheet: others are deleted.
      * 
      * @method fromJSON
      * @param {Object} data JSON representation of a notebook
      */
     Notebook.prototype.fromJSON = function (data) {
         var content = data.content;
         var ncells = this.ncells();
         var i;
         for (i=0; i<ncells; i++) {
             // Always delete cell 0 as they get renumbered as they are deleted.
             this.delete_cell(0);
         }
         // Save the metadata and name.
         this.metadata = content.metadata;
         this.notebook_name = data.name;
         var trusted = true;
         // Only handle 1 worksheet for now.
         var worksheet = content.worksheets[0];
         if (worksheet !== undefined) {
             if (worksheet.metadata) {
                 this.worksheet_metadata = worksheet.metadata;
             }
             var new_cells = worksheet.cells;
             ncells = new_cells.length;
             var cell_data = null;
             var new_cell = null;
             for (i=0; i<ncells; i++) {
                 cell_data = new_cells[i];
                 // VERSIONHACK: plaintext -> raw
                 // handle never-released plaintext name for raw cells
                 if (cell_data.cell_type === 'plaintext'){
                     cell_data.cell_type = 'raw';
                 }
 
                 new_cell = this.insert_cell_at_index(cell_data.cell_type, i);
                 new_cell.fromJSON(cell_data);
                 if (new_cell.cell_type == 'code' && !new_cell.output_area.trusted) {
                     trusted = false;
                 }
             }
         }
-        console.log('t', trusted, this.trusted);
         if (trusted != this.trusted) {
             this.trusted = trusted;
             $([IPython.events]).trigger("trust_changed.Notebook", trusted);
         }
         if (content.worksheets.length > 1) {
             IPython.dialog.modal({
                 title : "Multiple worksheets",
                 body : "This notebook has " + data.worksheets.length + " worksheets, " +
                     "but this version of IPython can only handle the first.  " +
                     "If you save this notebook, worksheets after the first will be lost.",
                 buttons : {
                     OK : {
                         class : "btn-danger"
                     }
                 }
             });
         }
     };
 
     /**
      * Dump this notebook into a JSON-friendly object.
      * 
      * @method toJSON
      * @return {Object} A JSON-friendly representation of this notebook.
      */
     Notebook.prototype.toJSON = function () {
         var cells = this.get_cells();
         var ncells = cells.length;
         var cell_array = new Array(ncells);
         var trusted = true;
         for (var i=0; i<ncells; i++) {
             var cell = cells[i];
             if (cell.cell_type == 'code' && !cell.output_area.trusted) {
                 trusted = false;
             }
             cell_array[i] = cell.toJSON();
         }
         var data = {
             // Only handle 1 worksheet for now.
             worksheets : [{
                 cells: cell_array,
                 metadata: this.worksheet_metadata
             }],
             metadata : this.metadata
         };
         if (trusted != this.trusted) {
             this.trusted = trusted;
             $([IPython.events]).trigger("trust_changed.Notebook", trusted);
         }
         return data;
     };
 
     /**
      * Start an autosave timer, for periodically saving the notebook.
      * 
      * @method set_autosave_interval
      * @param {Integer} interval the autosave interval in milliseconds
      */
     Notebook.prototype.set_autosave_interval = function (interval) {
         var that = this;
         // clear previous interval, so we don't get simultaneous timers
         if (this.autosave_timer) {
             clearInterval(this.autosave_timer);
         }
         
         this.autosave_interval = this.minimum_autosave_interval = interval;
         if (interval) {
             this.autosave_timer = setInterval(function() {
                 if (that.dirty) {
                     that.save_notebook();
                 }
             }, interval);
             $([IPython.events]).trigger("autosave_enabled.Notebook", interval);
         } else {
             this.autosave_timer = null;
             $([IPython.events]).trigger("autosave_disabled.Notebook");
         }
     };
     
     /**
      * Save this notebook on the server.
      * 
      * @method save_notebook
      */
     Notebook.prototype.save_notebook = function (extra_settings) {
         // Create a JSON model to be sent to the server.
         var model = {};
         model.name = this.notebook_name;
         model.path = this.notebook_path;
         model.content = this.toJSON();
         model.content.nbformat = this.nbformat;
         model.content.nbformat_minor = this.nbformat_minor;
         // time the ajax call for autosave tuning purposes.
         var start =  new Date().getTime();
         // We do the call with settings so we can set cache to false.
         var settings = {
             processData : false,
             cache : false,
             type : "PUT",
             data : JSON.stringify(model),
             headers : {'Content-Type': 'application/json'},
             success : $.proxy(this.save_notebook_success, this, start),
             error : $.proxy(this.save_notebook_error, this)
         };
         if (extra_settings) {
             for (var key in extra_settings) {
                 settings[key] = extra_settings[key];
             }
         }
         $([IPython.events]).trigger('notebook_saving.Notebook');
         var url = utils.url_join_encode(
             this.base_url,
             'api/notebooks',
             this.notebook_path,
             this.notebook_name
         );
         $.ajax(url, settings);
     };
     
     /**
      * Success callback for saving a notebook.
      * 
      * @method save_notebook_success
      * @param {Integer} start the time when the save request started
      * @param {Object} data JSON representation of a notebook
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.save_notebook_success = function (start, data, status, xhr) {
         this.set_dirty(false);
         $([IPython.events]).trigger('notebook_saved.Notebook');
         this._update_autosave_interval(start);
         if (this._checkpoint_after_save) {
             this.create_checkpoint();
             this._checkpoint_after_save = false;
         }
     };
     
     /**
      * update the autosave interval based on how long the last save took
      * 
      * @method _update_autosave_interval
      * @param {Integer} timestamp when the save request started
      */
     Notebook.prototype._update_autosave_interval = function (start) {
         var duration = (new Date().getTime() - start);
         if (this.autosave_interval) {
             // new save interval: higher of 10x save duration or parameter (default 30 seconds)
             var interval = Math.max(10 * duration, this.minimum_autosave_interval);
             // round to 10 seconds, otherwise we will be setting a new interval too often
             interval = 10000 * Math.round(interval / 10000);
             // set new interval, if it's changed
             if (interval != this.autosave_interval) {
                 this.set_autosave_interval(interval);
             }
         }
     };
     
     /**
      * Failure callback for saving a notebook.
      * 
      * @method save_notebook_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error HTTP error message
      */
     Notebook.prototype.save_notebook_error = function (xhr, status, error) {
         $([IPython.events]).trigger('notebook_save_failed.Notebook', [xhr, status, error]);
     };
 
     /**
      * Explicitly trust the output of this notebook.
      *
      * @method trust_notebook
      */
     Notebook.prototype.trust_notebook = function (extra_settings) {
-        // We do the call with settings so we can set cache to false.
-
-        var settings = {
-            processData : false,
-            cache : false,
-            type : "POST",
-            success : $.proxy(this._trust_notebook_success, this),
-            error : $.proxy(this._trust_notebook_error, this)
-        };
-        if (extra_settings) {
-            for (var key in extra_settings) {
-                settings[key] = extra_settings[key];
-            }
-        }
-
         var body = $("<div>").append($("<p>")
                 .text("A trusted IPython notebook may execute hidden malicious code ")
                 .append($("<strong>")
                     .append(
                         $("<em>").text("when you open it")
                     )
                 ).append(".")
             ).append($("<p>")
                 .text("For more information, see the ")
                 .append($("<a>").attr("href", "http://ipython.org/security.html")
                     .text("IPython security documentation")
                 ).append(".")
             );
 
         var nb = this;
         IPython.dialog.modal({
             title: "Trust this notebook?",
             body: body,
 
             buttons: {
                 Cancel : {},
                 Trust : {
                     class : "btn-danger",
                     click : function () {
-                        $([IPython.events]).trigger('notebook_trusting.Notebook');
-                        var url = utils.url_join_encode(
-                            nb.base_url,
-                            'api/notebooks',
-                            nb.notebook_path,
-                            nb.notebook_name,
-                            'trust'
-                        );
-                        $.ajax(url, settings);
+                        var cells = nb.get_cells();
+                        for (var i = 0; i < cells.length; i++) {
+                            var cell = cells[i];
+                            if (cell.cell_type == 'code') {
+                                cell.output_area.trusted = true;
+                            }
+                        }
+                        $([IPython.events]).on('notebook_saved.Notebook', function () {
+                            window.location.reload();
+                        });
+                        nb.save_notebook();
                     }
                 }
             }
         });
     };
 
-    Notebook.prototype._trust_notebook_success = function (data, status, xhr) {
-        $([IPython.events]).trigger('notebook_trusted.Notebook');
-        window.location.reload();
-    };
-
-    Notebook.prototype._trust_notebook_error = function (xhr, status, error) {
-        $([IPython.events]).trigger('notebook_trust_failed.Notebook', [xhr, status, error]);
-    };
-
     Notebook.prototype.new_notebook = function(){
         var path = this.notebook_path;
         var base_url = this.base_url;
         var settings = {
             processData : false,
             cache : false,
             type : "POST",
             dataType : "json",
             async : false,
             success : function (data, status, xhr){
                 var notebook_name = data.name;
                 window.open(
                     utils.url_join_encode(
                         base_url,
                         'notebooks',
                         path,
                         notebook_name
                     ),
                     '_blank'
                 );
             }
         };
         var url = utils.url_join_encode(
             base_url,
             'api/notebooks',
             path
         );
         $.ajax(url,settings);
     };
 
 
     Notebook.prototype.copy_notebook = function(){
         var path = this.notebook_path;
         var base_url = this.base_url;
         var settings = {
             processData : false,
             cache : false,
             type : "POST",
             dataType : "json",
             data : JSON.stringify({copy_from : this.notebook_name}),
             async : false,
             success : function (data, status, xhr) {
                 window.open(utils.url_join_encode(
                     base_url,
                     'notebooks',
                     data.path,
                     data.name
                 ), '_blank');
             }
         };
         var url = utils.url_join_encode(
             base_url,
             'api/notebooks',
             path
         );
         $.ajax(url,settings);
     };
 
     Notebook.prototype.rename = function (nbname) {
         var that = this;
         if (!nbname.match(/\.ipynb$/)) {
             nbname = nbname + ".ipynb";
         }
         var data = {name: nbname};
         var settings = {
             processData : false,
             cache : false,
             type : "PATCH",
             data : JSON.stringify(data),
             dataType: "json",
             headers : {'Content-Type': 'application/json'},
             success : $.proxy(that.rename_success, this),
             error : $.proxy(that.rename_error, this)
         };
         $([IPython.events]).trigger('rename_notebook.Notebook', data);
         var url = utils.url_join_encode(
             this.base_url,
             'api/notebooks',
             this.notebook_path,
             this.notebook_name
         );
         $.ajax(url, settings);
     };
 
     Notebook.prototype.delete = function () {
         var that = this;
         var settings = {
             processData : false,
             cache : false,
             type : "DELETE",
             dataType: "json",
         };
         var url = utils.url_join_encode(
             this.base_url,
             'api/notebooks',
             this.notebook_path,
             this.notebook_name
         );
         $.ajax(url, settings);
     };
 
     
     Notebook.prototype.rename_success = function (json, status, xhr) {
         var name = this.notebook_name = json.name;
         var path = json.path;
         this.session.rename_notebook(name, path);
         $([IPython.events]).trigger('notebook_renamed.Notebook', json);
     };
 
     Notebook.prototype.rename_error = function (xhr, status, error) {
         var that = this;
         var dialog = $('<div/>').append(
             $("<p/>").addClass("rename-message")
             .text('This notebook name already exists.')
         );
         $([IPython.events]).trigger('notebook_rename_failed.Notebook', [xhr, status, error]);
         IPython.dialog.modal({
             title: "Notebook Rename Error!",
             body: dialog,
             buttons : {
                 "Cancel": {},
                 "OK": {
                     class: "btn-primary",
                     click: function () {
                         IPython.save_widget.rename_notebook();
                 }}
                 },
             open : function (event, ui) {
                 var that = $(this);
                 // Upon ENTER, click the OK button.
                 that.find('input[type="text"]').keydown(function (event, ui) {
                     if (event.which === IPython.keyboard.keycodes.enter) {
                         that.find('.btn-primary').first().click();
                     }
                 });
                 that.find('input[type="text"]').focus();
             }
         });
     };
 
     /**
      * Request a notebook's data from the server.
      * 
      * @method load_notebook
      * @param {String} notebook_name and path A notebook to load
      */
     Notebook.prototype.load_notebook = function (notebook_name, notebook_path) {
         var that = this;
         this.notebook_name = notebook_name;
         this.notebook_path = notebook_path;
         // We do the call with settings so we can set cache to false.
         var settings = {
             processData : false,
             cache : false,
             type : "GET",
             dataType : "json",
             success : $.proxy(this.load_notebook_success,this),
             error : $.proxy(this.load_notebook_error,this),
         };
         $([IPython.events]).trigger('notebook_loading.Notebook');
         var url = utils.url_join_encode(
             this.base_url,
             'api/notebooks',
             this.notebook_path,
             this.notebook_name
         );
         $.ajax(url, settings);
     };
 
     /**
      * Success callback for loading a notebook from the server.
      * 
      * Load notebook data from the JSON response.
      * 
      * @method load_notebook_success
      * @param {Object} data JSON representation of a notebook
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.load_notebook_success = function (data, status, xhr) {
         this.fromJSON(data);
         if (this.ncells() === 0) {
             this.insert_cell_below('code');
             this.edit_mode(0);
         } else {
             this.select(0);
             this.command_mode();
         }
         this.set_dirty(false);
         this.scroll_to_top();
         if (data.orig_nbformat !== undefined && data.nbformat !== data.orig_nbformat) {
             var msg = "This notebook has been converted from an older " +
             "notebook format (v"+data.orig_nbformat+") to the current notebook " +
             "format (v"+data.nbformat+"). The next time you save this notebook, the " +
             "newer notebook format will be used and older versions of IPython " +
             "may not be able to read it. To keep the older version, close the " +
             "notebook without saving it.";
             IPython.dialog.modal({
                 title : "Notebook converted",
                 body : msg,
                 buttons : {
                     OK : {
                         class : "btn-primary"
                     }
                 }
             });
         } else if (data.orig_nbformat_minor !== undefined && data.nbformat_minor !== data.orig_nbformat_minor) {
             var that = this;
             var orig_vs = 'v' + data.nbformat + '.' + data.orig_nbformat_minor;
             var this_vs = 'v' + data.nbformat + '.' + this.nbformat_minor;
             var msg = "This notebook is version " + orig_vs + ", but we only fully support up to " +
             this_vs + ".  You can still work with this notebook, but some features " +
             "introduced in later notebook versions may not be available.";
 
             IPython.dialog.modal({
                 title : "Newer Notebook",
                 body : msg,
                 buttons : {
                     OK : {
                         class : "btn-danger"
                     }
                 }
             });
 
         }
         
         // Create the session after the notebook is completely loaded to prevent
         // code execution upon loading, which is a security risk.
         if (this.session === null) {
             this.start_session();
         }
         // load our checkpoint list
         this.list_checkpoints();
         
         // load toolbar state
         if (this.metadata.celltoolbar) {
             IPython.CellToolbar.global_show();
             IPython.CellToolbar.activate_preset(this.metadata.celltoolbar);
         }
         
         $([IPython.events]).trigger('notebook_loaded.Notebook');
     };
 
     /**
      * Failure callback for loading a notebook from the server.
      * 
      * @method load_notebook_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error HTTP error message
      */
     Notebook.prototype.load_notebook_error = function (xhr, status, error) {
         $([IPython.events]).trigger('notebook_load_failed.Notebook', [xhr, status, error]);
         var msg;
         if (xhr.status === 400) {
             msg = error;
         } else if (xhr.status === 500) {
             msg = "An unknown error occurred while loading this notebook. " +
             "This version can load notebook formats " +
             "v" + this.nbformat + " or earlier.";
         }
         IPython.dialog.modal({
             title: "Error loading notebook",
             body : msg,
             buttons : {
                 "OK": {}
             }
         });
     };
 
     /*********************  checkpoint-related  *********************/
     
     /**
      * Save the notebook then immediately create a checkpoint.
      * 
      * @method save_checkpoint
      */
     Notebook.prototype.save_checkpoint = function () {
         this._checkpoint_after_save = true;
         this.save_notebook();
     };
     
     /**
      * Add a checkpoint for this notebook.
      * for use as a callback from checkpoint creation.
      * 
      * @method add_checkpoint
      */
     Notebook.prototype.add_checkpoint = function (checkpoint) {
         var found = false;
         for (var i = 0; i < this.checkpoints.length; i++) {
             var existing = this.checkpoints[i];
             if (existing.id == checkpoint.id) {
                 found = true;
                 this.checkpoints[i] = checkpoint;
                 break;
             }
         }
         if (!found) {
             this.checkpoints.push(checkpoint);
         }
         this.last_checkpoint = this.checkpoints[this.checkpoints.length - 1];
     };
     
     /**
      * List checkpoints for this notebook.
      * 
      * @method list_checkpoints
      */
     Notebook.prototype.list_checkpoints = function () {
         var url = utils.url_join_encode(
             this.base_url,
             'api/notebooks',
             this.notebook_path,
             this.notebook_name,
             'checkpoints'
         );
         $.get(url).done(
             $.proxy(this.list_checkpoints_success, this)
         ).fail(
             $.proxy(this.list_checkpoints_error, this)
         );
     };
 
     /**
      * Success callback for listing checkpoints.
      * 
      * @method list_checkpoint_success
      * @param {Object} data JSON representation of a checkpoint
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.list_checkpoints_success = function (data, status, xhr) {
         data = $.parseJSON(data);
         this.checkpoints = data;
         if (data.length) {
             this.last_checkpoint = data[data.length - 1];
         } else {
             this.last_checkpoint = null;
         }
         $([IPython.events]).trigger('checkpoints_listed.Notebook', [data]);
     };
 
     /**
      * Failure callback for listing a checkpoint.
      * 
      * @method list_checkpoint_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error_msg HTTP error message
      */
     Notebook.prototype.list_checkpoints_error = function (xhr, status, error_msg) {
         $([IPython.events]).trigger('list_checkpoints_failed.Notebook');
     };
     
     /**
      * Create a checkpoint of this notebook on the server from the most recent save.
      * 
      * @method create_checkpoint
      */
     Notebook.prototype.create_checkpoint = function () {
         var url = utils.url_join_encode(
             this.base_url,
             'api/notebooks',
             this.notebook_path,
             this.notebook_name,
             'checkpoints'
         );
         $.post(url).done(
             $.proxy(this.create_checkpoint_success, this)
         ).fail(
             $.proxy(this.create_checkpoint_error, this)
         );
     };
 
     /**
      * Success callback for creating a checkpoint.
      * 
      * @method create_checkpoint_success
      * @param {Object} data JSON representation of a checkpoint
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.create_checkpoint_success = function (data, status, xhr) {
         data = $.parseJSON(data);
         this.add_checkpoint(data);
         $([IPython.events]).trigger('checkpoint_created.Notebook', data);
     };
 
     /**
      * Failure callback for creating a checkpoint.
      * 
      * @method create_checkpoint_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error_msg HTTP error message
      */
     Notebook.prototype.create_checkpoint_error = function (xhr, status, error_msg) {
         $([IPython.events]).trigger('checkpoint_failed.Notebook');
     };
     
     Notebook.prototype.restore_checkpoint_dialog = function (checkpoint) {
         var that = this;
         checkpoint = checkpoint || this.last_checkpoint;
         if ( ! checkpoint ) {
             console.log("restore dialog, but no checkpoint to restore to!");
             return;
         }
         var body = $('<div/>').append(
             $('<p/>').addClass("p-space").text(
                 "Are you sure you want to revert the notebook to " +
                 "the latest checkpoint?"
             ).append(
                 $("<strong/>").text(
                     " This cannot be undone."
                 )
             )
         ).append(
             $('<p/>').addClass("p-space").text("The checkpoint was last updated at:")
         ).append(
             $('<p/>').addClass("p-space").text(
                 Date(checkpoint.last_modified)
             ).css("text-align", "center")
         );
         
         IPython.dialog.modal({
             title : "Revert notebook to checkpoint",
             body : body,
             buttons : {
                 Revert : {
                     class : "btn-danger",
                     click : function () {
                         that.restore_checkpoint(checkpoint.id);
                     }
                 },
                 Cancel : {}
                 }
         });
     };
     
     /**
      * Restore the notebook to a checkpoint state.
      * 
      * @method restore_checkpoint
      * @param {String} checkpoint ID
      */
     Notebook.prototype.restore_checkpoint = function (checkpoint) {
         $([IPython.events]).trigger('notebook_restoring.Notebook', checkpoint);
         var url = utils.url_join_encode(
             this.base_url,
             'api/notebooks',
             this.notebook_path,
             this.notebook_name,
             'checkpoints',
             checkpoint
         );
         $.post(url).done(
             $.proxy(this.restore_checkpoint_success, this)
         ).fail(
             $.proxy(this.restore_checkpoint_error, this)
         );
     };
     
     /**
      * Success callback for restoring a notebook to a checkpoint.
      * 
      * @method restore_checkpoint_success
      * @param {Object} data (ignored, should be empty)
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.restore_checkpoint_success = function (data, status, xhr) {
         $([IPython.events]).trigger('checkpoint_restored.Notebook');
         this.load_notebook(this.notebook_name, this.notebook_path);
     };
 
     /**
      * Failure callback for restoring a notebook to a checkpoint.
      * 
      * @method restore_checkpoint_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error_msg HTTP error message
      */
     Notebook.prototype.restore_checkpoint_error = function (xhr, status, error_msg) {
         $([IPython.events]).trigger('checkpoint_restore_failed.Notebook');
     };
     
     /**
      * Delete a notebook checkpoint.
      * 
      * @method delete_checkpoint
      * @param {String} checkpoint ID
      */
     Notebook.prototype.delete_checkpoint = function (checkpoint) {
         $([IPython.events]).trigger('notebook_restoring.Notebook', checkpoint);
         var url = utils.url_join_encode(
             this.base_url,
             'api/notebooks',
             this.notebook_path,
             this.notebook_name,
             'checkpoints',
             checkpoint
         );
         $.ajax(url, {
             type: 'DELETE',
             success: $.proxy(this.delete_checkpoint_success, this),
             error: $.proxy(this.delete_notebook_error,this)
         });
     };
     
     /**
      * Success callback for deleting a notebook checkpoint
      * 
      * @method delete_checkpoint_success
      * @param {Object} data (ignored, should be empty)
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.delete_checkpoint_success = function (data, status, xhr) {
         $([IPython.events]).trigger('checkpoint_deleted.Notebook', data);
         this.load_notebook(this.notebook_name, this.notebook_path);
     };
 
     /**
      * Failure callback for deleting a notebook checkpoint.
      * 
      * @method delete_checkpoint_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error_msg HTTP error message
      */
     Notebook.prototype.delete_checkpoint_error = function (xhr, status, error_msg) {
         $([IPython.events]).trigger('checkpoint_delete_failed.Notebook');
     };
 
 
     IPython.Notebook = Notebook;
 
 
     return IPython;
 
 }(IPython));