事件：'finish'

【Event: 'finish'】

'finish' 事件来自 stream.Writable 类。调用 stream.end() 后并且所有数据块都已被 stream._transform() 处理，才会触发 'finish' 事件。如果发生错误，则不应触发 'finish'。

【The 'finish' event is from the stream.Writable class. The 'finish' event is emitted after stream.end() is called and all chunks have been processed by stream._transform(). In the case of an error, 'finish' should not be emitted.】