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>}`)
}
      if (this._stats) {
        this._stats.timeEnd("Rendering");
        this._stats.timeEnd("Overall");
      }
    };
    const internalRenderTask = new InternalRenderTask({
      callback: complete,
      
      params: {
        canvasContext,
        viewport,
        transform,
        imageLayer,
        background,
      },
      objs: this.objs,
      commonObjs: this.commonObjs,
      operatorList: intentState.operatorList,
      pageIndex: this._pageIndex,
      canvasFactory: canvasFactoryInstance,
      useRequestAnimationFrame: renderingIntent !== "print",
      pdfBug: this._pdfBug,
    });
    (intentState.renderTasks ||= new Set()).add(internalRenderTask);
    const renderTask = internalRenderTask.task;
    Promise.all([
      intentState.displayReadyCapability.promise,
      optionalContentConfigPromise,
    ])