code: def add_trigger(self, trigger):
          
          # Make sure triggers are re-sorted before a new reply can be requested
          self.sorted = False
  
          # If no trigger with this priority level has been defined yet, create a new list
          if trigger.priority not in self._triggers:
              self._triggers[trigger.priority] = [trigger]
              return
  
          # Otherwise, add this trigger to an existing priority list
          self._triggers[trigger.priority].append(trigger)
docs: Add a new trigger
          :param trigger: The Trigger object
          :type  trigger: Trigger