class DownloadHelper {

  public TrackGroupArray getTrackGroups(int periodIndex) {
    assertPreparedWithMedia();
    return trackGroupArrays[periodIndex];
  }

  public  DownloadHelper(
      String downloadType,
      Uri uri,
      @Nullable String cacheKey,
      @Nullable MediaSource mediaSource,
      DefaultTrackSelector.Parameters trackSelectorParameters,
      RendererCapabilities[] rendererCapabilities);

}