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>}`)
for (let i = 0, ii = operatorListChunk.length; i < ii; i++) {
      intentState.operatorList.fnArray.push(operatorListChunk.fnArray[i]);
      intentState.operatorList.argsArray.push(operatorListChunk.argsArray[i]);
    }
    intentState.operatorList.lastChunk = operatorListChunk.lastChunk;
    
    for (const internalRenderTask of intentState.renderTasks) {
      internalRenderTask.operatorListChanged();
    }
    if (operatorListChunk.lastChunk) {
      this._tryCleanup();
    }
  }
  /**
   * @private
   */
  _pumpOperatorList(args) {