Code comments for the example diffmpm.py

[Jiayao Yan]

Hello difftaichi Team,

First of all, I'd like to extend my gratitude for developing and maintaining such an innovative and impactful project.

While working with the difftaichi examples, I've been particularly focusing on the diffmpm.py file. While the functionality and performance of this script are impressive, I've found that the lack of comments makes it challenging to understand and extend certain parts of the code, especially for newcomers.

Understanding the underlying principles and the rationale behind certain coding decisions can significantly enhance the learning curve. Therefore, I kindly request if it would be possible to add some comments to the diffmpm.py file.

Thank you,

JYan