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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 send_simple_command(self, cmd):
 """Send simple mqtt commands."""

        pkt = MqttPkt()
        
        pkt.command = cmd
        pkt.remaining_length = 0
        
        ret = pkt.alloc()
        if ret != NC.ERR_SUCCESS:
            return ret
        
        return self.packet_queue(pkt)