Groupby Agg not working if different partials with same name on the same column
- [x] closes #28570
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them
- [x] whatsnew entry
a unit test was added in accordance with issue [28570](https://github.com/pandas-dev/pandas/issues/28570). It asserts the equality of the expected output with the tested df. 


Hello @aliraeisdanaei! 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 2022-01-10 15:17:01 UTC Hey, this is my first pull request to pandas, so please do tell me if I have made any mistakes. 

Thank you & God bless,
Ali Raeisdanaei @jbrockmendel Thanks for the feedback.  Thanks for the PR, but it appears to have gone stale. If you'd like to continue and investigate the bug fix, please ping and we can reopen.