issue_comments: 1212214557

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https://github.com/pydata/xarray/issues/6836#issuecomment-1212214557 https://api.github.com/repos/pydata/xarray/issues/6836 1212214557 IC_kwDOAMm_X85IQO0d 2448579 2022-08-11T16:28:10Z 2022-08-11T16:36:35Z MEMBER

@benbovy I tracked this down to

``` python

mda.one.to_index()

v2022.06.0

MultiIndex([('a', 0), ('a', 1), ('b', 0), ('b', 1), ('c', 0), ('c', 1)], names=['one', 'two'])

v2022.03.0

Index(['a', 'a', 'b', 'b', 'c', 'c'], dtype='object', name='x') ```

We call to_index here in safe_cast_to_index: https://github.com/pydata/xarray/blob/f8fee902360f2330ab8c002d54480d357365c172/xarray/core/utils.py#L115-L140

Not sure if the fix should be only in the GroupBy specifically or more generally in safe_cast_to_index

The GroupBy context is https://github.com/pydata/xarray/blob/f8fee902360f2330ab8c002d54480d357365c172/xarray/core/groupby.py#L434

 
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