How deep do you plan on going?
I think it would be invaluable if you create such diagrams to show you where exactly in the mid/low level APIs or the callback system certain stuff is implemented.
If you’re not familiar with the internals of the library, it can get a bit tricky to find certain bits of code, especially since they’re usually split up into multiple different functions that call each other (not complaining).
For example, it took me quite some time to realise that opt.zero_grad() is called in the Learner’s one_batch(). I spent the better part of an hour looking for it in multiple callbacks – this probably speaks more to my inefficiency, but I’m sure I’m not alone here 
If (when) done right, I think a visual guide like yours could help alleviate some of the issues brought up in the forum post below, and make it generally easier to hack around within the framework.