TYP: groupby.pyi
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry

@jbrockmendel you may have answered this, but how do we tests / keep these up to date? > but how do we tests / keep these up to date?

@simonjayhawkins has a branch (though i dont see a PR) that implements tests, but im not sure exactly how that works.  as for keeping it up to date: manually > @simonjayhawkins has a branch (though i dont see a PR) that implements tests

#40202 - closed until after arrow string array is further progressed.
 > as for keeping it up to date: manually

related issue #28133