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 文件及其 Examples 區段，然後檢視已記錄的 TarFile 方法，找出需要隨機存取的操作。在適用的地方記錄串流模式的限制，並加入一個示範串流模式的範例，確保產生的文件清楚指出無法使用的操作。