Enable `colors` as list in `plot.pie()`

[danielhuppmann]

Please confirm that this PR has done the following:

• [x] Tests Added
• [x] Documentation Added
• ~Name of contributors Added to AUTHORS.rst~
• [x] Description in RELEASE_NOTES.md Added

Description of PR

This PR enables passing an explicit colors arg as list to to the pie plot, see https://matplotlib.org/stable/api/_as_gen/matplotlib.pyplot.pie.html

It also implements the title keyword argument, which was previously ignored in the implementation, and future-proofs pandas (using min(level=0) will be disabled).

[codecov[bot]]

Codecov Report

Merging #563 (c4b7935) into main (32fcd33) will increase coverage by 0.0%. The diff coverage is 100.0%.

@@          Coverage Diff          @@
##            main    #563   +/-   ##
=====================================
  Coverage   93.6%   93.7%           
=====================================
  Files         50      50           
  Lines       5313    5322    +9     
=====================================
+ Hits        4978    4987    +9     
  Misses       335     335           

Impacted Files	Coverage Δ
pyam/plotting.py	92.9% <100.0%> (+<0.1%)	:arrow_up:
tests/test_plotting.py	100.0% <100.0%> (ø)

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[danielhuppmann]

Thanks for the suggestions, all implemented!

Not quite sure what you mean by adding a test for resolving a future-warning? If you go back to a previous test run, section "Test with pytest", line 270, there is a warning that this particular code will stop working. If you compare this to the current test runs, this warning is gone. (There are plenty of others, though, tackling them one at a time).

[gidden]

Not quite sure what you mean by adding a test for resolving a future-warning? If you go back to a previous test run, section "Test with pytest", line 270, there is a warning that this particular code will stop working. If you compare this to the current test runs, this warning is gone. (There are plenty of others, though, tackling them one at a time).

Specifically the line

mins = pd.concat([allmins, intermins]).groupby(level=0).min()

I was curious it is was possible to add any test for this. If not, that's fine.

[gidden]

Ahh ok, I understand now. Thanks!