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.messageHandler.sendWithPromise("GetFieldObjects", null);
  }
  hasJSActions() {
    return (this._hasJSActionsPromise ||= this.messageHandler.sendWithPromise(
      "HasJSActions",
      null
    ));
  }
  getCalculationOrderIds() {
    return this.messageHandler.sendWithPromise("GetCalculationOrderIds", null);
  }
  getDestinations() {
    return this.messageHandler.sendWithPromise("GetDestinations", null);
  }
  getDestination(id) {
    if (typeof id !== "string") {
      return Promise.reject(new Error("Invalid destination request."));
    }
    return this.messageHandler.sendWithPromise("GetDestination", {
      id,
    });
  }
  getPageLabels() {
    return this.messageHandler.sendWithPromise("GetPageLabels", null);
  }
  getPageLayout() {
    return this.messageHandler.sendWithPromise("GetPageLayout", null);
  }
  getPageMode() {