Add comments and type hints to python code

The python code current has nearly zero comments, which makes it difficult for people to figure out what the code is actually doing. Having comments would make it easier for people who are less familar with python and this specific codebase to contribute. Type hints would also be a useful addition for similar reasons.

Issue 中没有指出文件、测试或入口点。首先定位仓库中的 Python 代码并确定其范围；当相关 Python 代码包含有助于贡献者理解其行为的实用注释和类型提示时，即表示完成。

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