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._pageIndex + 1;
  }
  /**
   * @type {number} The number of degrees the page is rotated clockwise.
   */
  get rotate() {
    return this._pageInfo.rotate;
  }
  /**
   * @type {Object} The reference that points to this page. It has `num` and
   *   `gen` properties.
   */
  get ref() {
    return this._pageInfo.ref;
  }
  /**
   * @type {number} The default size of units in 1/72nds of an inch.
   */
  get userUnit() {
    return this._pageInfo.userUnit;
  }
  /**
   * @type {Array<number>} An array of the visible portion of the PDF page in
   *   user space units [x1, y1, x2, y2].
   */
  get view() {