def test_applicationDataBeforeSubnegotiation(self):
        """
        Application bytes received before a subnegotiation command are
        delivered before the negotiation is processed.
        """
        self._deliver(
            b'z' + telnet.IAC + telnet.SB + b'Qx' + telnet.IAC + telnet.SE,
            ('bytes', b'z'), ('negotiate', b'Q', [b'x']))

        Application bytes received before a subnegotiation command are
        delivered before the negotiation is processed.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_telnet.py