def make_checksum(message):
    """Calculates checksum for specified message.

    :param message: ASTM message.
    :type message: bytes

    :returns: Checksum value that is actually byte sized integer in hex base
    :rtype: bytes
    """
    if not isinstance(message[0], int):
        message = map(ord, message)
    return hex(sum(message) & 255)[2:].upper().zfill(2).encode()
