docs: @Deprecated
      protected <T extends Listener> void removeInternal(Class<T> listenerClass,
              Iterator<Object> it) {
          final Object next = it.next();
          final T listener = listenerClass.cast(next);
          it.remove();
          final RegistrationEvent e = new RegistrationEvent(this, listenerClass);
          listener.onUnregister(e);
      }