[Python] Implement docstrings and testing

Currently the library has a lot of code dumped throughout that has no documentation associated to explain what it does. Additionally, there is no real testing in place to ensure older methods are not broken by never changes etc.

Therefor, implementing correct docstrings throughout the code and implementing proper testing would be a good way to bring up the quality of the library.

该 issue 未列出任何文件、测试或入口点。首先调研 Python 库，以确定 docstring 和回归测试的范围；完成要求包括为代码编写文档，并提供能够保护现有方法的有意义测试。