def test_proxyDeleteAttribute(self):
        """
        The attributes that proxy objects proxy should be deletable and affect
        the original object.
        """
        yayable = Yayable()
        yayable.ifaceAttribute = None
        proxy = proxyForInterface(IProxiedInterface)(yayable)
        del proxy.ifaceAttribute
        self.assertFalse(hasattr(yayable, 'ifaceAttribute'))

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