DOC: Updated the docstring of Series.rank / DataFrame.rank

[EdAbati]

• passes git diff upstream/master -u -- "*.py" | flake8 --diff

I have updated the docstring following the convention and I have added some examples.

Please let me know if I can further improve this.

Thanks

[pep8speaks]

Hello @EdAbati! Thanks for submitting the PR.

• There are no PEP8 issues in the file pandas/core/generic.py !

[WillAyd]

Thanks for the submission!

[datapythonista]

Besides the comments, there are pep8 issues in all the examples.

[codecov]

Codecov Report

Merging #23263 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #23263   +/-   ##
=======================================
  Coverage   92.24%   92.24%           
=======================================
  Files         161      161           
  Lines       51339    51339           
=======================================
  Hits        47360    47360           
  Misses       3979     3979

Flag	Coverage Δ
#multiple	90.64% <ø> (ø)	⬆️
#single	42.34% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/core/generic.py	96.82% <ø> (ø)	⬆️

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[datapythonista]

Thanks for the work @EdAbati, I was checking the examples in more detail, and for me doesn't make it very easy to understand what rank does. Added some comments on how I think we could make them more clear. But fix them in a way that they make sense for you, and that they would be useful for you if you wanted to learn what rank does and you didn't know already.

[datapythonista]

@EdAbati do you have time to update this PR?

[jreback]

ping @datapythonista

[datapythonista]

Closing as stale, @EdAbati let us know if you want to continue working on it.

[EdAbati]

Hi @datapythonista,

Extremely sorry for the delay.
I have been very busy in the last month or so.
I was planning to come back to this one next when I will be on holiday.

[EdAbati]

Hi @datapythonista ,

I gave it another try.
I have opened another pull request where I have made the changes requested above.