Selectivly add some additional xrefs to dunders in contextlib docs

Author: CAM-Gerlach

Doc/library/contextlib.rst

@@ -228,7 +228,7 @@ Functions and classes provided:
 
 .. function:: nullcontext(enter_result=None)
 
-   Return a context manager that returns *enter_result* from ``__enter__``, but
+   Return a context manager that returns *enter_result* from :meth:`~object.__enter__`, but
    otherwise does nothing. It is intended to be used as a stand-in for an
    optional context manager, for example::
 
@@ -335,7 +335,7 @@ Functions and classes provided:
    For example, the output of :func:`help` normally is sent to *sys.stdout*.
    You can capture that output in a string by redirecting the output to an
    :class:`io.StringIO` object. The replacement stream is returned from the
-   ``__enter__`` method and so is available as the target of the
+   :meth:`~object.__enter__` method and so is available as the target of the
    :keyword:`with` statement::
 
         with redirect_stdout(io.StringIO()) as f:
@@ -396,7 +396,8 @@ Functions and classes provided:
    A base class that enables a context manager to also be used as a decorator.
 
    Context managers inheriting from ``ContextDecorator`` have to implement
-   ``__enter__`` and ``__exit__`` as normal. ``__exit__`` retains its optional
+   :meth:`~object.__enter__` and :meth:`~object.__exit__` as normal.
+   ``__exit__`` retains its optional
    exception handling even when used as a decorator.
 
    ``ContextDecorator`` is used by :func:`contextmanager`, so you get this
@@ -710,9 +711,9 @@ context management protocol.
 Catching exceptions from ``__enter__`` methods
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-It is occasionally desirable to catch exceptions from an ``__enter__``
+It is occasionally desirable to catch exceptions from an :meth:`~object.__enter__`
 method implementation, *without* inadvertently catching exceptions from
-the :keyword:`with` statement body or the context manager's ``__exit__``
+the :keyword:`with` statement body or the context manager's :meth:`~object.__exit__`
 method. By using :class:`ExitStack` the steps in the context management
 protocol can be separated slightly in order to allow this::