Does it come with any samples on how to use it? Like, how to train, how to generate after training, etc.

Eh, sort of: https://github.com/rowanz/grover It can't be that difficult if OP did it so quickly, after all.

If you want much more detailed documentation, I wrote up in detail how to train & generate text with the original GPT-2 models using nshepperd's codebase: https://www.gwern.net/GPT-2

minimaxr also has a actively maintained codebase which I believe has powered some of the GPT-2 projects you might've seen recently like Talk to Transformer: https://github.com/minimaxir/gpt-2-simple

Thank you so much!