static getAllStreamsFromManifest_(manifest) {
    /** @type {!Set<shaka.extern.Stream>} */
    const set = new Set();

    for (const variant of manifest.variants) {
      if (variant.audio) {
        set.add(variant.audio);
      }
      if (variant.video) {
        set.add(variant.video);
      }
    }

    for (const text of manifest.textStreams) {
      set.add(text);
    }

    for (const image of manifest.imageStreams) {
      set.add(image);
    }

    return set;
  }
Get the set of all streams in |manifest|.

@param {shaka.extern.Manifest} manifest
@return {!Set<shaka.extern.Stream>}
@private