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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def pack_mbap(transaction_id, protocol_id, length, unit_id):
 """ Create and return response MBAP. :param transaction_id: Transaction id. :param protocol_id: Protocol id. :param length: Length of following bytes in ADU. :param unit_id: Unit id. :return: Byte array of 7 bytes. """

    return struct.pack('>HHHB', transaction_id, protocol_id, length, unit_id)