Add a new trigger
        :param trigger: The Trigger object
        :type  trigger: Trigger

def add_trigger(self, trigger):
        """
        Add a new trigger
        :param trigger: The Trigger object
        :type  trigger: 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)