code: def set_qos(self, port_name, type='linux-htb', max_rate=None, queues=None):
          
          queues = queues if queues else []
          command_qos = ovs_vsctl.VSCtlCommand(
              'set-qos',
              [port_name, type, max_rate])
          command_queue = ovs_vsctl.VSCtlCommand(
              'set-queue',
              [port_name, queues])
          self.run_command([command_qos, command_queue])
          if command_qos.result and command_queue.result:
              return command_qos.result + command_queue.result
          return None
docs: Sets a Qos rule and creates Queues on the given port.