Resources to understand PyTorch source code

Hello ! I wanted to ask if there are any good resources (may include books, articles, blog posts, videos, courses etc) that discuss the implementation details and source code explanations(of PyTorch, example - how to get started with the source code) for beginners. Please let me know if there are any :innocent:. Asking this because newbies get scared looking at such a large code base and it feels daunting to contribute (but there is just so much willingness to contribute).