code: def fire_event(self, event_name, service_name, default=None):
          
          service = self.get_service(service_name)
          callbacks = service.get(event_name, default)
          if not callbacks:
              return
          if not isinstance(callbacks, Iterable):
              callbacks = [callbacks]
          for callback in callbacks:
              if isinstance(callback, ManagerCallback):
                  callback(self, service_name, event_name)
              else:
                  callback(service_name)
docs: Fire a data_ready, data_lost, start, or stop event on a given service.