CLN: Break up aggregate.transform

[rhshadrach]

• closes #xxxx
• tests added / passed
• passes black pandas
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

Precursor to #36478. Just breaks up transform without any code changes.

[arw2019]

Just an idea but it looks like we have a bunch of functions with the same signature which differ by the type of func arg. Would it make sense to use single dispatch?

[rhshadrach]

Thanks for the suggestion @arw2019. In this particular case, I think not. In #36478, we'll change e.g. isinstance(func, dict) to using is_dict_like. I believe that makes singledispatch not viable.

[arw2019]

Thanks for the suggestion @arw2019. In this particular case, I think not. In #36478, we'll change e.g. isinstance(func, dict) to using is_dict_like. I believe that makes singledispatch not viable.

Right, that makes sense.

Another question, should transform_dict_like and transform_str_or_callable be underscored? Since AFAICT they're private methods

[jreback]

Thanks for the suggestion @arw2019. In this particular case, I think not. In #36478, we'll change e.g. isinstance(func, dict) to using is_dict_like. I believe that makes singledispatch not viable.

Right, that makes sense.

Another question, should transform_dict_like and transform_str_or_callable be underscored? Since AFAICT they're private methods

this entire hierarchy is private pandas/core/* (yes it doesn't actually look like it, but its been document this way for a long time)

[jreback]

thanks @rhshadrach

happy to have typing passes as well