stream.PassThrough 类

stream.PassThrough 类是 Transform 流的简单实现，它只是将输入字节传到输出。 它的目的主要是用于示例和测试，但在某些用例中，stream.PassThrough 可用作新型流的构建块。

The stream.PassThrough class is a trivial implementation of a Transform stream that simply passes the input bytes across to the output. Its purpose is primarily for examples and testing, but there are some use cases where stream.PassThrough is useful as a building block for novel sorts of streams.