def test_ciphers(self):
        """
        Test that the client and server play nicely together, in all
        the various combinations of ciphers.
        """
        deferreds = []
        for cipher in transport.SSHTransportBase.supportedCiphers + [b'none']:
            def setCipher(proto):
                proto.supportedCiphers = [cipher]
                return proto
            deferreds.append(self._runClientServer(setCipher))
        return defer.DeferredList(deferreds, fireOnOneErrback=True)

        Test that the client and server play nicely together, in all
        the various combinations of ciphers.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_transport.py