https://github.com/mozilla/pdf.js/blob/0df1a5661958df0c4ed2f73b0f3266d825c5c280/src/display/api.js#L710-L719
The return type signature `@returns {Promise<{num: number, gen: number}>}` is mismatched with its definition. (should be `@returns {Promise<number>}`)
if (!this._annotationsPromise || this._annotationsIntent !== intent) {
      this._annotationsPromise = this._transport.getAnnotations(
        this._pageIndex,
        intent
      );
      this._annotationsIntent = intent;
    }
    return this._annotationsPromise;
  }
  /**
   * @returns {Promise<Object>} A promise that is resolved with an
   *   {Object} with JS actions.
   */
  getJSActions() {