class DownloadHelper {

  public int getPeriodCount() {
    if (mediaSource == null) {
      return 0;
    }
    assertPreparedWithMedia();
    return trackGroupArrays.length;
  }

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

}