bpo-20180: itertools.groupby Argument Clinic conversion by taleinat · Pull Request #4170 · python/cpython
This PR contains a small part of the changes from PR #4117, which applies an extensive Argument Clinic conversion to all of Modules/itertoolsmodule.c.
In an effort to streamline the process of reviewing that conversion, this PR only converts the groupby class and the internal _grouper helper class. It also only converts the constructors, avoiding conversion of private methods such as __reduce__ and __setstate__. Finally, it minimizes the doc-string changes, whereas the original PR mentioned above made significant changes to doc-strings in some cases.