async function getStoredManifest(uri) {
    /** @type {!shaka.offline.ManifestConverter} */
    const converter = new shaka.offline.ManifestConverter(
        uri.mechanism(), uri.cell());

    /** @type {!shaka.offline.StorageMuxer} */
    const muxer = new shaka.offline.StorageMuxer();

    try {
      await muxer.init();
      const cell = await muxer.getCell(uri.mechanism(), uri.cell());
      const manifests = await cell.getManifests([uri.key()]);
      const manifest = manifests[0];

      goog.asserts.assert(manifest, 'A manifest should have been found');
      return converter.fromManifestDB(manifest);
    } finally {
      await muxer.destroy();
    }
  }
@param {!shaka.offline.OfflineUri} uri
@return {!Promise<shaka.extern.Manifest>}