sclass VMBusListenerWithLivelinessCheck implements IF2<S, O, O> {
  Set listeners; // where we were added
  IF0<Bool> livelinessCheck;
  O listener;
  
  *(Set *listeners, IF0<Bool> *livelinessCheck, O *listener) {}
  *(Set *listeners, IF0<Bool> *livelinessCheck, IVF2<S, O> *listener) {}
  
  public O get(S msg, O arg) {
    if (livelinessCheck != null && !livelinessCheck.get()) {
      ifdef VMBusListenerWithLivelinessCheck_debug
        print VMBusListenerWithLivelinessCheck("Removing VM bus listener");
      endifdef
      remove(listeners, this);
    }
    ret callF(listener, msg, arg);
  }
}