Bug 29764 groupby loses index name sometimes #36121
                
     Merged
            
            
          
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black pandasgit diff upstream/master -u -- "*.py" | flake8 --diffIssue was fixed for sum and any with c9144ca.
So the only thing left was to add the index name in
_wrap_transformed_output. I kept the tests from #33111, to show, that alle cases are now handled correctly.I hope it is okay, to add a new PR for this?