DOC/TYP: Fixed typing and doc
- [x] xref https://github.com/pandas-dev/pandas/pull/33263#pullrequestreview-389118991
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

@MomIsBestFriend can you rebase (and address any actionable comments) Thanks @MomIsBestFriend closing as stale. ping to reopen.