def test_mutualExclusionExcludesByKeyword(self):
        """
        L{mutuallyExclusiveArguments} raises a L{TypeError}n if its
        decoratee is passed a pair of mutually exclusive arguments.
        """
        @_mutuallyExclusiveArguments([['a', 'b']])
        def func(a=3, b=4):
            return a + b

        self.assertRaises(TypeError, func, a=3, b=4)

        L{mutuallyExclusiveArguments} raises a L{TypeError}n if its
        decoratee is passed a pair of mutually exclusive arguments.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/test/test_deprecate.py