Give TypeError if calling 'update', etc. from Model instance instead of from class
Related to https://github.com/coleifer/peewee/issues/1192 This grosses up the code quite a bit. They already have the classmethod decorator. I agree that it grosses up the code a bit. But it's very useful.

Oh well, it's your repo.
   The grossness isn't a reflection of your coding ability, I should make that clear -- it's just one of those problems that requires a kinda gnarly fix. Thanks for the patch, I'm sorry if it was wasted time on your part.
I hit a snag with this that took me hours to debug. Since these methods really only make sense as class methods, I don't think you should to be able to call them from an instance.