class DownloadContext {

    public AlterContext alter() {
        return new AlterContext(this);
    }

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

}