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>}`)
.then(([transparency, optionalContentConfig]) => {
        if (this.pendingCleanup) {
          complete();
          return;
        }
        if (this._stats) {
          this._stats.time("Rendering");
        }
        internalRenderTask.initializeGraphics({
          transparency,
          optionalContentConfig,
        });
        internalRenderTask.operatorListChanged();
      })
      .catch(complete);
    return renderTask;
  }
  /**
   * @returns {Promise<PDFOperatorList>} A promise resolved with an
   *   {@link PDFOperatorList} object that represents page's operator list.
   */
  getOperatorList() {
    function operatorListChanged() {
      if (intentState.operatorList.lastChunk) {
        intentState.opListReadCapability.resolve(intentState.operatorList);
        intentState.renderTasks.delete(opListTask);
      }
    }
    const renderingIntent = "oplist";
    let intentState = this._intentStates.get(renderingIntent);