Compose a SCS message

        body: list containing the body of the message.
        returns: full telegram expressed (bytes instance)

def compose_telegram(body):
    """ Compose a SCS message

        body: list containing the body of the message.
        returns: full telegram expressed (bytes instance)
    """

    msg = [b"A8"] + body + [checksum_bytes(body)] + [b"A3"]
    return str.encode("".join([x.decode() for x in msg]))