BUG: nlargest/nsmallest can now consider nan values like sort_values(ascending=True).head(n)
- [x] closes #28984 
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [x] whatsnew entry

nsmallest/nlargest are now consistent with x.sort_values(ascending=False).head(n)/x.sort_values(ascending=True).head(n)
Edit: I've changed test_nlargest_misc(self) in \tests\serie\methods\test_nlargest.py to reflect the fact that Nans are included

Hello @usersblock! 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 2021-09-07 07:41:45 UTC @usersblock i've closed #42997 as a duplicate of #28984, can you update the references to the issue also include the code sample from #28984 as a test. Updated reference and added new test to test_nlargest.py in frames\methods ok can you add a replica of the test in the OP for `df.groupby('grp').apply(lambda x: x.sort_values('z', ascending=False).head(1))` thanks @usersblock very nice!