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>}`)
this._readyCapability.resolve();
  }
  requestDataRange(begin, end) {
    unreachable("Abstract method PDFDataRangeTransport.requestDataRange");
  }
  abort() {}
}
/**
 * Proxy to a `PDFDocument` in the worker thread.
 */
class PDFDocumentProxy {
  constructor(pdfInfo, transport) {
    this._pdfInfo = pdfInfo;
    this._transport = transport;
  }
  /**
   * @type {AnnotationStorage} Storage for annotation data in forms.
   */
  get annotationStorage() {
    return this._transport.annotationStorage;
  }
  /**
   * @type {number} Total number of pages in the PDF file.
   */
  get numPages() {