def test_noAnswerResponderAskedForAnswer(self):
        """
        Verify that responders with requiresAnswer=False will actually respond
        if the client sets requiresAnswer=True.  In other words, verify that
        requiresAnswer is a hint honored only by the client.
        """
        c, s, p = connectedServerAndClient(
            ServerClass=NoAnswerCommandProtocol,
            ClientClass=SimpleSymmetricCommandProtocol)
        L = []
        c.callRemote(Hello, hello=b"Hello!").addCallback(L.append)
        p.flush()
        self.assertEqual(len(L), 1)
        self.assertEqual(L, [dict(hello=b"Hello!-noanswer",
                                   Print=None)])  # Optional response argument

        Verify that responders with requiresAnswer=False will actually respond
        if the client sets requiresAnswer=True.  In other words, verify that
        requiresAnswer is a hint honored only by the client.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_amp.py