def test_writeSequence(self):
        """
        L{TuntapPort.writeSequence} sends a datagram into the tunnel by
        concatenating the byte strings in the list passed to it.
        """
        datagram = [b"a", b"b", b"c", b"d"]
        self.port.startListening()
        self.port.writeSequence(datagram)
        self.assertEqual(
            self.system.getTunnel(self.port).writeBuffer,
            deque([b"".join(datagram)]))

        L{TuntapPort.writeSequence} sends a datagram into the tunnel by
        concatenating the byte strings in the list passed to it.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/pair/test/test_tuntap.py