def bytes(cls):
        """
        Bytes which are expected when encoding an instance constructed using
        C{kwargs} and which are expected to result in an identical instance when
        decoded.

        @return: The L{bytes} of a wire encoded message.
        """
        return (
            b'\x00\x00' # ID: 0
            b'\x00' # QR: 0, OPCODE: 0, AA: 0, TC: 0, RD: 0
            b'\x00' # RA: 0, Z, RCODE: 0
            b'\x00\x01' # Queries count
            b'\x00\x00' # Anwers count
            b'\x00\x00' # Authority count
            b'\x00\x01' # Additionals count

            # Queries
            b'\x03www\x07example\x03com\x00' # QNAME
            b'\x00\x01' # QTYPE (A)
            b'\x00\x01' # QCLASS (IN)

            # Additional OPT record
            b'\x00' # NAME (.)
            b'\x00\x29' # TYPE (OPT 41)
            b'\x10\x00' # UDP Payload Size (4096)
            b'\x00' # Extended RCODE
            b'\x03' # EDNS version
            b'\x00\x00' # DO: False + Z
            b'\x00\x00' # RDLENGTH
        )

        Bytes which are expected when encoding an instance constructed using
        C{kwargs} and which are expected to result in an identical instance when
        decoded.

        @return: The L{bytes} of a wire encoded message.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/test/test_dns.py