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._internalRenderTask.cancel();
  }
}
/**
 * For internal use only.
 * @ignore
 */
const InternalRenderTask = (function InternalRenderTaskClosure() {
  const canvasInRendering = new WeakSet();
  
  class InternalRenderTask {
    constructor({
      callback,
      params,
      objs,
      commonObjs,
      operatorList,
      pageIndex,
      canvasFactory,
      useRequestAnimationFrame = false,
      pdfBug = false,
    }) {
      this.callback = callback;