getStreamsFromSets_(disabled, adaptationSets, contentType) {
    if (disabled || !adaptationSets.length) {
      return [];
    }

    return adaptationSets.reduce((all, part) => {
      if (part.contentType != contentType) {
        return all;
      }

      all.push(...part.streams);
      return all;
    }, []);
  }
Gets the streams from the given sets or returns an empty array if disabled
or no streams are found.
@param {boolean} disabled
@param {!Array<!shaka.dash.DashParser.AdaptationInfo>} adaptationSets
@param {string} contentType
@private