tarfile stream restrictions should be documented

Documentation

tarfile documentation mentions stream mode only in tarfile.open, and says "However, such a TarFile object is limited in that it does not allow random access, see Examples."

The examples section does not showcase stream mode at all.

I believe all methods that might be unavailable in stream mode should be documented as such.

先查看 tarfile.open 文档及其 Examples 部分，然后检查已记录的 TarFile 方法，找出需要随机访问的操作。在适用的地方记录流模式的限制，并添加一个演示流模式的示例，确保生成的文档明确标识不可用的操作。