Rearrange the NotebookManager methods for clarity

Methods are organized into three categories:
 - Methods that must be implemented in subclasses
 - Methods that have default implementations, but can
   be overridden if required.
 - Support methods meant to be called by methods in subclasses

IPython/html/services/notebooks/nbmanager.py

@@ -47,26 +47,9 b' class NotebookManager(LoggingConfigurable):'
     def _notary_default(self):
         return sign.NotebookNotary(parent=self)
     
-    def check_and_sign(self, nb, path, name):
-        """Check for trusted cells, and sign the notebook.
-        
-        Called as a part of saving notebooks.
-        """
-        if self.notary.check_cells(nb):
-            self.notary.sign(nb)
-        else:
-            self.log.warn("Saving untrusted notebook %s/%s", path, name)
-    
-    def mark_trusted_cells(self, nb, path, name):
-        """Mark cells as trusted if the notebook signature matches.
-        
-        Called as a part of loading notebooks.
-        """
-        trusted = self.notary.check_signature(nb)
-        if not trusted:
-            self.log.warn("Notebook %s/%s is not trusted", path, name)
-        self.notary.mark_cells(nb, trusted)
-    
+    # NotebookManager API part 1: methods that must be
+    # implemented in subclasses.
+
     def path_exists(self, path):
         """Does the API-style path (directory) actually exist?
         
@@ -101,47 +84,6 b' class NotebookManager(LoggingConfigurable):'
         """
         raise NotImplementedError
 
-    def _notebook_dir_changed(self, name, old, new):
-        """Do a bit of validation of the notebook dir."""
-        if not os.path.isabs(new):
-            # If we receive a non-absolute path, make it absolute.
-            self.notebook_dir = os.path.abspath(new)
-            return
-        if os.path.exists(new) and not os.path.isdir(new):
-            raise TraitError("notebook dir %r is not a directory" % new)
-        if not os.path.exists(new):
-            self.log.info("Creating notebook dir %s", new)
-            try:
-                os.mkdir(new)
-            except:
-                raise TraitError("Couldn't create notebook dir %r" % new)
-
-    # Main notebook API
-
-    def increment_filename(self, basename, path=''):
-        """Increment a notebook filename without the .ipynb to make it unique.
-        
-        Parameters
-        ----------
-        basename : unicode
-            The name of a notebook without the ``.ipynb`` file extension.
-        path : unicode
-            The URL path of the notebooks directory
-
-        Returns
-        -------
-        name : unicode
-            A notebook name (with the .ipynb extension) that starts
-            with basename and does not refer to any existing notebook.
-        """
-        path = path.strip('/')
-        for i in itertools.count():
-            name = u'{basename}{i}{ext}'.format(basename=basename, i=i,
-                                                ext=self.filename_ext)
-            if not self.notebook_exists(name, path):
-                break
-        return name
-
     def notebook_exists(self, name, path=''):
         """Returns a True if the notebook exists. Else, returns False.
 
@@ -207,6 +149,55 b' class NotebookManager(LoggingConfigurable):'
         """Delete notebook by name and path."""
         raise NotImplementedError('must be implemented in a subclass')
 
+    def create_checkpoint(self, name, path=''):
+        """Create a checkpoint of the current state of a notebook
+        
+        Returns a checkpoint_id for the new checkpoint.
+        """
+        raise NotImplementedError("must be implemented in a subclass")
+    
+    def list_checkpoints(self, name, path=''):
+        """Return a list of checkpoints for a given notebook"""
+        return []
+    
+    def restore_checkpoint(self, checkpoint_id, name, path=''):
+        """Restore a notebook from one of its checkpoints"""
+        raise NotImplementedError("must be implemented in a subclass")
+
+    def delete_checkpoint(self, checkpoint_id, name, path=''):
+        """delete a checkpoint for a notebook"""
+        raise NotImplementedError("must be implemented in a subclass")
+    
+    def info_string(self):
+        return "Serving notebooks"
+
+    # NotebookManager API part 2: methods that have useable default
+    # implementations, but can be overridden in subclasses.
+
+    def increment_filename(self, basename, path=''):
+        """Increment a notebook filename without the .ipynb to make it unique.
+        
+        Parameters
+        ----------
+        basename : unicode
+            The name of a notebook without the ``.ipynb`` file extension.
+        path : unicode
+            The URL path of the notebooks directory
+
+        Returns
+        -------
+        name : unicode
+            A notebook name (with the .ipynb extension) that starts
+            with basename and does not refer to any existing notebook.
+        """
+        path = path.strip('/')
+        for i in itertools.count():
+            name = u'{basename}{i}{ext}'.format(basename=basename, i=i,
+                                                ext=self.filename_ext)
+            if not self.notebook_exists(name, path):
+                break
+        return name
+
     def create_notebook(self, model=None, path=''):
         """Create a new notebook and return its model with no content."""
         path = path.strip('/')
@@ -236,29 +227,43 b' class NotebookManager(LoggingConfigurable):'
         model = self.save_notebook(model, to_name, path)
         return model
     
-    # Checkpoint-related
-    
-    def create_checkpoint(self, name, path=''):
-        """Create a checkpoint of the current state of a notebook
+    def log_info(self):
+        self.log.info(self.info_string())
+
+    # NotebookManager methods provided for use in subclasses.
+
+    def check_and_sign(self, nb, path, name):
+        """Check for trusted cells, and sign the notebook.
         
-        Returns a checkpoint_id for the new checkpoint.
+        Called as a part of saving notebooks.
         """
-        raise NotImplementedError("must be implemented in a subclass")
+        if self.notary.check_cells(nb):
+            self.notary.sign(nb)
+        else:
+            self.log.warn("Saving untrusted notebook %s/%s", path, name)
     
-    def list_checkpoints(self, name, path=''):
-        """Return a list of checkpoints for a given notebook"""
-        return []
+    def mark_trusted_cells(self, nb, path, name):
+        """Mark cells as trusted if the notebook signature matches.
+        
+        Called as a part of loading notebooks.
+        """
+        trusted = self.notary.check_signature(nb)
+        if not trusted:
+            self.log.warn("Notebook %s/%s is not trusted", path, name)
+        self.notary.mark_cells(nb, trusted)
     
-    def restore_checkpoint(self, checkpoint_id, name, path=''):
-        """Restore a notebook from one of its checkpoints"""
-        raise NotImplementedError("must be implemented in a subclass")
+    def _notebook_dir_changed(self, name, old, new):
+        """Do a bit of validation of the notebook dir."""
+        if not os.path.isabs(new):
+            # If we receive a non-absolute path, make it absolute.
+            self.notebook_dir = os.path.abspath(new)
+            return
+        if os.path.exists(new) and not os.path.isdir(new):
+            raise TraitError("notebook dir %r is not a directory" % new)
+        if not os.path.exists(new):
+            self.log.info("Creating notebook dir %s", new)
+            try:
+                os.mkdir(new)
+            except:
+                raise TraitError("Couldn't create notebook dir %r" % new)
 
-    def delete_checkpoint(self, checkpoint_id, name, path=''):
-        """delete a checkpoint for a notebook"""
-        raise NotImplementedError("must be implemented in a subclass")
-    
-    def log_info(self):
-        self.log.info(self.info_string())
-    
-    def info_string(self):
-        return "Serving notebooks"