class DownloadContext {

    public void startOnParallel(DownloadListener listener) {
        start(listener, false);
    }

      DownloadContext(@NonNull DownloadTask[] tasks,
                    @Nullable DownloadContextListener contextListener,
                    @NonNull QueueSet set,
                    @NonNull Handler uiHandler);
      DownloadContext(@NonNull DownloadTask[] tasks,
                    @Nullable DownloadContextListener contextListener,
                    @NonNull QueueSet set);

}