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._transport.getMetadata();
  }
  /**
   * @typedef {Object} MarkInfo
   * Properties correspond to Table 321 of the PDF 32000-1:2008 spec.
   * @property {boolean} Marked
   * @property {boolean} UserProperties
   * @property {boolean} Suspects
   */
  /**
   * @returns {Promise<MarkInfo | null>} A promise that is resolved with
   *   a {MarkInfo} object that contains the MarkInfo flags for the PDF
   *   document, or `null` when no MarkInfo values are present in the PDF file.
   */
  getMarkInfo() {
    return this._transport.getMarkInfo();
  }
  /**
   * @returns {Promise<TypedArray>} A promise that is resolved with a
   *   {TypedArray} that has the raw data from the PDF.
   */
  getData() {