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>}`)
const intentState = this._intentStates.get(intent);
    if (!intentState) {
      return; 
    }
    if (this._stats) {
      this._stats.timeEnd("Page Request");
    }
    
    
    if (intentState.displayReadyCapability) {
      intentState.displayReadyCapability.resolve(transparency);
    }
  }
  /**
   * @private
   */
  _renderPageChunk(operatorListChunk, intentState) {