@tchambers As a general library? None that come even remotely close and the closer you get, the harder they are to use.
I glanced through the one you linked to and spotted several problems in about a minute that would make it non-compliant (e.g., the possible plurality of generator, or how it can be an obect and not just a string, etc https://www.w3.org/TR/activitystreams-vocabulary/#dfn-generator).
But there are some that may be getting there with specific implementations of AP, it's just that they are working with implementations.