automatically get the current axes instance

[aloctavodia]

• Follows official PR format
• Includes a sample plot to visually illustrate the changes (only for plot-related functions)
• Includes new or updated tests to cover the new feature
• Code style correct (follows pylint and black guidelines)
• Changes are listed in changelog

This recover the old behavior, allowing to do this, without the need to explicitly need to pass the axes

a= np.random.normal(0, 1, 100)
b= np.random.normal(0, 1, 100)
az.plot_kde(a)
az.plot_kde(b)

[codecov]

Codecov Report

Merging #1452 (6718341) into master (d529c8b) will decrease coverage by 0.00%.
The diff coverage is 93.33%.

@@            Coverage Diff             @@
##           master    #1452      +/-   ##
==========================================
- Coverage   91.94%   91.93%   -0.01%     
==========================================
  Files         105      105              
  Lines       11216    11228      +12     
==========================================
+ Hits        10312    10323      +11     
- Misses        904      905       +1     

Impacted Files	Coverage Δ
arviz/plots/backends/matplotlib/hdiplot.py	92.59% <80.00%> (-3.06%)	⬇️
arviz/plots/backends/matplotlib/distplot.py	95.45% <100.00%> (+0.29%)	⬆️
arviz/plots/backends/matplotlib/kdeplot.py	98.80% <100.00%> (+0.05%)	⬆️
arviz/data/datasets.py	98.38% <0.00%> (ø)

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[ahartikainen]

This will get only 1 axis?

Should this go inside create axis grid with some keyword flag?

Can this access also figure -> axes?

[aloctavodia]

This will get only one axis but that's the case when you do something like

az.plot_kde(a)
az.plot_kde(b)

For more complex stuff you will need to pass the axes as usual, as is the case for the rest of our plots.