def test_KEXINIT_groupexchange(self):
        """
        KEXINIT packet with a group-exchange key exchange results
        in a KEX_DH_GEX_REQUEST message.
        """
        self.proto.supportedKeyExchanges = [self.kexAlgorithm]
        self.proto.dataReceived(self.transport.value())
        # The response will include our advertised group sizes.
        self.assertEqual(self.packets, [(
            transport.MSG_KEX_DH_GEX_REQUEST,
            b'\x00\x00\x04\x00\x00\x00\x08\x00\x00\x00\x20\x00')])

        KEXINIT packet with a group-exchange key exchange results
        in a KEX_DH_GEX_REQUEST message.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_transport.py