class DownloadListener4 implements DownloadListener,
        Listener4Assist.Listener4Callback, ListenerAssist {

    public void setAssistExtend(@NonNull Listener4Assist.AssistExtend assistExtend) {
        this.assist.setAssistExtend(assistExtend);
    }

      DownloadListener4(Listener4Assist assist);
    public  DownloadListener4();

}