code: protected function triggerListeners(EventInterface $event, callable $callback = null)
      {
          if (!$event instanceof DependencyResultEvent) {
              throw new \InvalidArgumentException('This event manager only accepts events of the type ' . DependencyResultEvent::class);
          }
  
          $results = parent::triggerListeners($event, $callback);
  
          $dependencies = $event->getDependencyResultCollection();
  
          foreach ($results as $result) {
              if (null !== $result) {
                  try {
                      $dependencies->add($result);
                  }
                  /* silently ignore all invalid results */
                  catch (\UnexpectedValueException $e) {
                  } catch (\InvalidArgumentException $e) {
                  }
              }
          }
  
          return $results;
      }
docs: Triggers listeners.
  
  Loops over the responses and tries to add any non empty response as a DepnendecyResult to the collection.
  
  @param EventInterface $event
  @param callable|null  $callback
  
  @return \Zend\EventManager\ResponseCollection
  @throws \InvalidArgumentException if the event is not an instance of DependencyResultEvent