ENH: named agg with multiple columns
- [ ] closes #29268
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

pls add tests always

in fact tests should be done before any code changes to make sure they behave properly  Thanks for the heads up @jreback , actually I was hoping to get some feedback which was the reason I pushed this as a draft while developing to get some comments. Some parts are challenging since I am not sure if I make the right decisions. Hello @erfannariman! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:







There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2021-09-12 11:44:58 UTC @jreback @ivanovmg I made some progress, but I am at the point that I need to pass the DataFrame as a obj to the aggregator instead of a Series so we can do the aggregation over the columns. This pull request is stale because it has been open for thirty days with no activity. Please update or respond to this comment if you're still interested in working on this. @erfannariman status here? > @erfannariman status here?

This went stale, but is definitely one I would like very much to finish. I just think it gets quite complex on some points where I could use some guidance. Will take asap to clean up, merge master etc so it's updated. @erfannariman Can you merge master/update? Thanks. Thanks @erfannariman for the PR. closing as stale. ping if you want to continue. > Thanks @erfannariman for the PR. closing as stale. ping if you want to continue.

Started to work on this PR again, can you re-open? Thanks @simonjayhawkins  this is quite old, happen to reopen if actively worked on.