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>}`)
return (this._jsActionsPromise ||= this._transport.getPageJSActions(
      this._pageIndex
    ));
  }
  /**
   * @returns {Promise<Object | null>} A promise that is resolved with
   *   an {Object} with a fake DOM object (a tree structure where elements
   *   are {Object} with a name, attributes (class, style, ...), value and
   *   children, very similar to a HTML DOM tree), or `null` if no XFA exists.
   */
  getXfa() {
    return (this._xfaPromise ||= this._transport.getPageXfa(this._pageIndex));
  }
  /**
   * Begins the process of rendering a page to the desired context.
   *
   * @param {RenderParameters} params Page render parameters.
   * @returns {RenderTask} An object that contains a promise that is
   *   resolved when the page finishes rendering.
   */
  render({