PERF: use _get_axis_number instead of if axis in [...]
Added _get_axis_number in style.py as per the standards 

Hello @KiranHipparagi! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:



There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2021-08-30 18:44:10 UTC A pr for this was already merged  @phofl yes i know but there is one more change we need look at..
```
axis = self.data._get_axis_number(axis)            <-- PR
result = data.apply(func, axis=0, **kwargs) if axis == 0 
    else (data.T.apply(func, axis=0, **kwargs).T if axis == 1 
    else func(data, **kwargs))
       
 if axis in [0, "index"]:                           <--master
         result = data.apply(func, axis=0, **kwargs)
 elif axis in [1, "columns"]:
         result = data.T.apply(func, axis=0, **kwargs).T  # see GH 42005
 else:
     result = func(data, **kwargs)
``` Please resolve conflicts first  @phofl thanks for the clarification.please review i have resolved conflicts. -1. I like it the way it is. As @phofl states this has already had a recent PR fix. @attack68 @phofl Thanks for the clarification.I'm new to open source project.Is there any file left for modification apart from style.py? @KiranHipparagi did a quick search, it seems outside of tests, this is pretty clean actually. Do find another issue marked "good first issue".