def test_proxyDescriptorGet(self):
        """
        _ProxyDescriptor's __get__ method should return the appropriate
        attribute of its argument's 'original' attribute if it is invoked with
        an object.  If it is invoked with None, it should return a false
        class-method emulator instead.

        For some reason, Python's documentation recommends to define
        descriptors' __get__ methods with the 'type' parameter as optional,
        despite the fact that Python itself never actually calls the descriptor
        that way.  This is probably do to support 'foo.__get__(bar)' as an
        idiom.  Let's make sure that the behavior is correct.  Since we don't
        actually use the 'type' argument at all, this test calls it the
        idiomatic way to ensure that signature works; test_proxyInheritance
        verifies the how-Python-actually-calls-it signature.
        """
        class Sample(object):
            called = False
            def hello(self):
                self.called = True
        fakeProxy = Sample()
        testObject = Sample()
        fakeProxy.original = testObject
        pd = components._ProxyDescriptor("hello", "original")
        self.assertEqual(pd.__get__(fakeProxy), testObject.hello)
        fakeClassMethod = pd.__get__(None)
        fakeClassMethod(fakeProxy)
        self.assertTrue(testObject.called)

        _ProxyDescriptor's __get__ method should return the appropriate
        attribute of its argument's 'original' attribute if it is invoked with
        an object.  If it is invoked with None, it should return a false
        class-method emulator instead.

        For some reason, Python's documentation recommends to define
        descriptors' __get__ methods with the 'type' parameter as optional,
        despite the fact that Python itself never actually calls the descriptor
        that way.  This is probably do to support 'foo.__get__(bar)' as an
        idiom.  Let's make sure that the behavior is correct.  Since we don't
        actually use the 'type' argument at all, this test calls it the
        idiomatic way to ensure that signature works; test_proxyInheritance
        verifies the how-Python-actually-calls-it signature.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/test/test_components.py