def test_receiveUnimplemented(self):
        """
        Test that unimplemented messages are received correctly.  See
        test_sendUnimplemented.
        """
        self.proto.dispatchMessage(transport.MSG_UNIMPLEMENTED,
                                   b'\x00\x00\x00\xff')
        self.assertEqual(self.proto.unimplementeds, [255])

        Test that unimplemented messages are received correctly.  See
        test_sendUnimplemented.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_transport.py