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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 _create_request_adu(slave_id, req_pdu):
 """ Return request ADU for Modbus RTU. :param slave_id: Slave id. :param req_pdu: Byte array with PDU. :return: Byte array with ADU. """

    first_part_adu = struct.pack('>B', slave_id) + req_pdu

    return first_part_adu + get_crc(first_part_adu)