fix docs of custommagics (#14478)

While trying to implement custom magic I stumbled upon error while
trying to import decorators. I found that wrong module is mentioned and
decided to fix that.

docs/source/config/custommagics.rst

@@ -1,212 +1,212 b''
 .. _defining_magics:
 
 Defining custom magics
 ======================
 
 There are two main ways to define your own magic functions: from standalone
 functions and by inheriting from a base class provided by IPython:
 :class:`IPython.core.magic.Magics`. Below we show code you can place in a file
 that you load from your configuration, such as any file in the ``startup``
 subdirectory of your default IPython profile.
 
 First, let us see the simplest case. The following shows how to create a line
 magic, a cell one and one that works in both modes, using just plain functions:
 
 .. sourcecode:: python
 
     from IPython.core.magic import (register_line_magic, register_cell_magic,
                                     register_line_cell_magic)
 
     @register_line_magic
     def lmagic(line):
         "my line magic"
         return line
 
     @register_cell_magic
     def cmagic(line, cell):
         "my cell magic"
         return line, cell
 
     @register_line_cell_magic
     def lcmagic(line, cell=None):
         "Magic that works both as %lcmagic and as %%lcmagic"
         if cell is None:
             print("Called as line magic")
             return line
         else:
             print("Called as cell magic")
             return line, cell
 
     # In an interactive session, we need to delete these to avoid
     # name conflicts for automagic to work on line magics.
     del lmagic, lcmagic
 
 
 You can also create magics of all three kinds by inheriting from the
 :class:`IPython.core.magic.Magics` class.  This lets you create magics that can
 potentially hold state in between calls, and that have full access to the main
 IPython object:
     
 .. sourcecode:: python
 
     # This code can be put in any Python module, it does not require IPython
     # itself to be running already.  It only creates the magics subclass but
     # doesn't instantiate it yet.
     from __future__ import print_function
     from IPython.core.magic import (Magics, magics_class, line_magic,
                                     cell_magic, line_cell_magic)
 
     # The class MUST call this class decorator at creation time
     @magics_class
     class MyMagics(Magics):
 
         @line_magic
         def lmagic(self, line):
             "my line magic"
             print("Full access to the main IPython object:", self.shell)
             print("Variables in the user namespace:", list(self.shell.user_ns.keys()))
             return line
 
         @cell_magic
         def cmagic(self, line, cell):
             "my cell magic"
             return line, cell
 
         @line_cell_magic
         def lcmagic(self, line, cell=None):
             "Magic that works both as %lcmagic and as %%lcmagic"
             if cell is None:
                 print("Called as line magic")
                 return line
             else:
                 print("Called as cell magic")
                 return line, cell
 
 
     # In order to actually use these magics, you must register them with a
     # running IPython.
 
     def load_ipython_extension(ipython):
         """
         Any module file that define a function named `load_ipython_extension`
         can be loaded via `%load_ext module.path` or be configured to be
         autoloaded by IPython at startup time.
         """
         # You can register the class itself without instantiating it.  IPython will
         # call the default constructor on it.
         ipython.register_magics(MyMagics)
 
 If you want to create a class with a different constructor that holds
 additional state, then you should always call the parent constructor and
 instantiate the class yourself before registration:
 
 .. sourcecode:: python
 
     @magics_class
     class StatefulMagics(Magics):
         "Magics that hold additional state"
 
         def __init__(self, shell, data):
             # You must call the parent constructor
             super(StatefulMagics, self).__init__(shell)
             self.data = data
         
         # etc...
 
     def load_ipython_extension(ipython):
         """
         Any module file that define a function named `load_ipython_extension`
         can be loaded via `%load_ext module.path` or be configured to be
         autoloaded by IPython at startup time.
         """
         # This class must then be registered with a manually created instance,
         # since its constructor has different arguments from the default:
         magics = StatefulMagics(ipython, some_data)
         ipython.register_magics(magics)
 
 
 .. note::
 
    In early IPython versions 0.12 and before the line magics were
    created using a :func:`define_magic` API function.  This API has been
    replaced with the above in IPython 0.13 and then completely removed
    in IPython 5.  Maintainers of IPython extensions that still use the
    :func:`define_magic` function are advised to adjust their code
    for the current API.
 
 
 Accessing user namespace and local scope
 ========================================
 
 When creating line magics, you may need to access surrounding scope  to get user
 variables (e.g when called inside functions). IPython provides the
 ``@needs_local_scope`` decorator that can be imported from
-``IPython.core.magics``. When decorated with ``@needs_local_scope`` a magic will
+``IPython.core.magic``. When decorated with ``@needs_local_scope`` a magic will
 be passed ``local_ns`` as an argument. As a convenience ``@needs_local_scope``
 can also be applied to cell magics even if cell magics cannot appear at local
 scope context.
 
 Silencing the magic output
 ==========================
 
 Sometimes it may be useful to define a magic that can be silenced the same way
 that non-magic expressions can, i.e., by appending a semicolon at the end of the Python
 code to be executed. That can be achieved by decorating the magic function with
 the decorator ``@output_can_be_silenced`` that can be imported from
-``IPython.core.magics``. When this decorator is used, IPython will parse the Python
+``IPython.core.magic``. When this decorator is used, IPython will parse the Python
 code used by the magic and, if the last token is a ``;``, the output created by the
 magic will not show up on the screen. If you want to see an example of this decorator
 in action, take a look on the ``time`` magic defined in
 ``IPython.core.magics.execution.py``.
 
 Complete Example
 ================
 
 Here is a full example of a magic package. You can distribute magics using
 setuptools, distutils, or any other distribution tools like `flit
 <https://flit.readthedocs.io>`_ for pure Python packages.
 
 When distributing magics as part of a package, recommended best practice is to
 execute the registration inside the `load_ipython_extension` as demonstrated in
 the example below, instead of directly in the module (as in the initial example
 with the ``@register_*`` decorators). This means a user will need to explicitly
 choose to load your magic with ``%load_ext``. instead implicitly getting it when
 importing the module. This is particularly relevant if loading your magic has 
 side effects, if it is slow to load, or if it might override another magic with
 the same name. 
 
 .. sourcecode:: bash
 
    .
    ├── example_magic
    │   ├── __init__.py
    │   └── abracadabra.py
    └── setup.py
 
 .. sourcecode:: bash
 
    $ cat example_magic/__init__.py
    """An example magic"""
    __version__ = '0.0.1'
    
    from .abracadabra import Abracadabra
    
    def load_ipython_extension(ipython):
        ipython.register_magics(Abracadabra)
 
 .. sourcecode:: bash
 
     $ cat example_magic/abracadabra.py
     from IPython.core.magic import (Magics, magics_class, line_magic, cell_magic)
 
     @magics_class
     class Abracadabra(Magics):
 
         @line_magic
         def abra(self, line):
             return line
 
         @cell_magic
         def cadabra(self, line, cell):
             return line, cell