TYP: pd.eval, DataFrame.(eval, query) 
- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

xref https://github.com/pandas-dev/pandas/pull/38416#discussion_r546736072
@arw2019 can you address @jbrockmendel comments. Needs rebase and a couple of comments are outstanding, but otherwise I think this is pretty close. @jbrockmendel over to you. @MarcoGorelli feel free to push or otherwise close. I was going to close as stale but @jbrockmendel commented it was pretty close. https://github.com/pandas-dev/pandas/pull/38625#issuecomment-808916410 closing as stale.