it turns out adapter-transformers actually has a mutated entire copy of the transformers repository inside it, and replaces this on the user's system. they update this regularly, but their current version does not have longt5.
i added longt5 and forked the repo and pushed it. it doesn't work with adapters yet until the instructiosn at https://github.com/adapter-hub/adapter-transformers/blob/master/adapter_docs/contributing/adding_adapters_to_a_model.md are followed i'm interested in trying following these for a little bit
