code: @Override
      public <T extends EventListener> void subscribe(EventPublisher source, T listener) {
  	checkPermission();
  	if (source == null || listener == null) {
  	    throw new IllegalArgumentException("Parameters cannot be null");
  	}
  	super.subscribe(source, listener);
      }
docs: /* (non-Javadoc)
  @see com.github.thehilikus.events.event_manager.SubscriptionManager#subscribe(com.github.thehilikus.events.event_manager.api.EventPublisher, java.util.EventListener)