class DownloadListener4 implements DownloadListener,
        Listener4Assist.Listener4Callback, ListenerAssist {

    @Override
    public final void fetchProgress(@NonNull DownloadTask task, int blockIndex,
                                    long increaseBytes) {
        assist.fetchProgress(task, blockIndex, increaseBytes);
    }

      DownloadListener4(Listener4Assist assist);
    public  DownloadListener4();

}