Stateful transforms are simple objects with member functions that maintain state across calls:
下载虎嗅APP，第一时间获取深度独到的商业科技资讯，连接更多创新人群与线下活动
，这一点在WPS官方版本下载中也有详细论述
controller.enqueue(processChunk(chunk));，详情可参考51吃瓜
assert d["1"] is None, "Sanity prevails! 😌"