def test_proxySetAttribute(self):
        """
        The attributes that proxy objects proxy should be assignable and affect
        the original object.
        """
        yayable = Yayable()
        proxy = proxyForInterface(IProxiedInterface)(yayable)
        thingy = object()
        proxy.ifaceAttribute = thingy
        self.assertIs(yayable.ifaceAttribute, thingy)

        The attributes that proxy objects proxy should be assignable and affect
        the original object.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/test/test_components.py