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.

该 issue 没有指定任何文件、测试或入口点。首先盘点 Python 代码并确定哪些模块属于范围，然后一致地添加注释和类型提示；完成的标准是已记录约定的范围，且更新后的代码仍能正常运行。

由索引模型根据 Issue 内容生成。