class Listener1Assist implements ListenerAssist,
        ListenerModelHandler.ModelCreator<Listener1Assist.Listener1Model> {

    public void taskEnd(DownloadTask task, EndCause cause, @Nullable Exception realCause) {
        Listener1Model model = modelHandler.removeOrCreate(task, task.getInfo());
        if (callback != null) callback.taskEnd(task, cause, realCause, model);
    }

    public  Listener1Assist();
      Listener1Assist(ListenerModelHandler<Listener1Model> handler);

}