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.params = params;
      this.objs = objs;
      this.commonObjs = commonObjs;
      this.operatorListIdx = null;
      this.operatorList = operatorList;
      this._pageIndex = pageIndex;
      this.canvasFactory = canvasFactory;
      this._pdfBug = pdfBug;
      this.running = false;
      this.graphicsReadyCallback = null;
      this.graphicsReady = false;
      this._useRequestAnimationFrame =
        useRequestAnimationFrame === true && typeof window !== "undefined";
      this.cancelled = false;
      this.capability = createPromiseCapability();
      this.task = new RenderTask(this);
      
      this._cancelBound = this.cancel.bind(this);
      this._continueBound = this._continue.bind(this);
      this._scheduleNextBound = this._scheduleNext.bind(this);
      this._nextBound = this._next.bind(this);
      this._canvas = params.canvasContext.canvas;
    }
    get completed() {
      return this.capability.promise.catch(function () {
        
        
      });
    }
    initializeGraphics({ transparency = false, optionalContentConfig }) {