Ask HN: Good Python Machine Learning Codebases to read?

Hi everyone! Looking for codebases in Python doing machine learning to follow the practice of reading high quality code as a way to improve (not looking for framework or library codebases but codebases that are trying to solve problems - e.g. recommendation system for movies, etc.)

Would be a bonus to have well structured and commented code (not new to programming or machine learning but looking to improve)

(Partially inspired by this thread - https://news.ycombinator.com/item?id=9896369)

Thanks!