/**
  * @param MappedEventSubscriber $subscriber
  * @param EventManager          $manager
  * @param Reader|null           $reader
  */
 protected function addSubscriber(MappedEventSubscriber $subscriber, EventManager $manager, Reader $reader = null)
 {
     if ($reader) {
         $subscriber->setAnnotationReader($reader);
     }
     $manager->addEventSubscriber($subscriber);
 }