REF: use _get_axis_number instead of if axis in [...]: #43048
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry

this is being addressed in #43127.

Please find one of the many examples of code to fix that someone else has not already submitted a PR for.