def test_lookupSubsystem_data(self):
        """
        After having looked up a subsystem, data should be passed along to the
        client.  Additionally, subsystems were passed the entire request packet
        as data, instead of just the additional data.

        We check for the additional tidle to verify that the data passed
        through the client.
        """
        #self.session.dataReceived('1')
        # subsystems didn't get extended data
        #self.session.extReceived(connection.EXTENDED_DATA_STDERR, '2')

        self.session.requestReceived(b'subsystem',
                                     common.NS(b'TestSubsystem') + b'data')

        self.assertEqual(self.session.conn.data[self.session],
                [b'\x00\x00\x00\x0dTestSubsystemdata~'])
        self.session.dataReceived(b'more data')
        self.assertEqual(self.session.conn.data[self.session][-1],
                b'more data~')

        After having looked up a subsystem, data should be passed along to the
        client.  Additionally, subsystems were passed the entire request packet
        as data, instead of just the additional data.

        We check for the additional tidle to verify that the data passed
        through the client.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_session.py