CLN: Remove MultiIndex._get_grouper_for_level

[codamuse]

• closes CLN: Remove MultiIndex._get_grouper_for_level #49452 (Replace xxxx with the GitHub issue number)
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

[codamuse]

@rhshadrach Cleaner branch and passes tests locally (hopefully CI will work). Is there a reason though to even keep _get_grouper_for_level around or use it in the Grouping class? Around L483 in gouper.py I think I could just set self.grouping_vector = index_level.map(mapper) and achieve the same outcome. Nothing else uses _get_grouper_for_level() so is there a need to keep it around at all?

[jbrockmendel]

@codamuse can you address the linting failures and merge main

[codamuse]

@codamuse can you address the linting failures and merge main

@jbrockmendel updated. Do you think _get_grouper_for_level() makes sense to keep around? I don't think the name is even reflective of what that function does anymore (no levels to get a grouper and level isn't even an accepted argument). Since it's only used in grouper.py L483 would it be cleaner to simplify and change L483 to:

self.grouping_vector = index_level.map(mapper)

while dropping _get_grouper_for_level() or deprecating it some other way just in case?

None of the above reflected in this PR, just wondering why not do it that way.

[jbrockmendel]

[...] would it be cleaner to simplify and change [...]

seems reasonable.

[jbrockmendel]

LGTM pending green. Love to see more simplifications in grouper.py

[rhshadrach]

lgtm

[rhshadrach]

Thanks @codamuse - very nice!