mathlib

3c755273 - lint(group_theory/*): docstrings and an inhabited instance (#4493)

lint(group_theory/*): docstrings and an inhabited instance (#4493) An inhabited instance for `presented_group` Docstrings in `group_theory/abelianization` and `group_theory/congruence`. Co-authored-by: Aaron Anderson <65780815+awainverse@users.noreply.github.com> Co-authored-by: Bryan Gin-ge Chen <bryangingechen@gmail.com>