def test_keyexchanges(self):
        """
        Like test_ciphers, but for the various key exchanges.
        """
        deferreds = []
        for kexAlgorithm in transport.SSHTransportBase.supportedKeyExchanges:
            def setKeyExchange(proto):
                proto.supportedKeyExchanges = [kexAlgorithm]
                return proto
            deferreds.append(self._runClientServer(setKeyExchange))
        return defer.DeferredList(deferreds, fireOnOneErrback=True)

        Like test_ciphers, but for the various key exchanges.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_transport.py