Thanks. Sorry for the lack of documentation. The first version (Branch 0.1.x) was more focused as a proof of concept. Despite the examples, after some time I found several limitations. That lead to a branch (kill_the_baby), witch i've restarted the project. Well, lack of documentation first started due the constant changes over the time. pyNES 0.2.x will have a more mature API and a DOC.
Maybe someone else can document it if the creator doesn't have time.
At any rate, I'm happy it exists, getting a toy game running on actual hardware will be hilariously fun for me, if it works. I don't mind using the code as the documentation for something this obscure if docs aren't available. Better than having to spend time learning 6502 assembly just for screwing around with NES games (or NES demoscene, hmm... it's probably cheating but it'll be fun.)