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>}`)
constructor(messageHandler, loadingTask, networkStream, params) {
    this.messageHandler = messageHandler;
    this.loadingTask = loadingTask;
    this.commonObjs = new PDFObjects();
    this.fontLoader = new FontLoader({
      docId: loadingTask.docId,
      onUnsupportedFeature: this._onUnsupportedFeature.bind(this),
      ownerDocument: params.ownerDocument,
    });
    this._params = params;
    this.CMapReaderFactory = new params.CMapReaderFactory({
      baseUrl: params.cMapUrl,
      isCompressed: params.cMapPacked,
    });
    this.destroyed = false;
    this.destroyCapability = null;
    this._passwordCapability = null;
    this._networkStream = networkStream;
    this._fullReader = null;
    this._lastProgress = null;
    this.pageCache = [];
    this.pagePromises = [];
    this.downloadInfoCapability = createPromiseCapability();
    this.setupMessageHandler();
  }
  get annotationStorage() {