def test_deprecatedUpdatesDocstring(self):
        """
        The docstring of the deprecated function is appended with information
        about the deprecation.
        """

        def localDummyCallable():
            """
            Do nothing.

            This is used to test the deprecation decorators.
            """

        version = Version('Twisted', 8, 0, 0)
        dummy = deprecated(version)(localDummyCallable)

        _appendToDocstring(
            localDummyCallable,
            _getDeprecationDocstring(version, ''))

        self.assertEqual(localDummyCallable.__doc__, dummy.__doc__)

        The docstring of the deprecated function is appended with information
        about the deprecation.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/test/test_deprecate.py