Compacity metric

[Francesco-Marini]

Description

This PR creates a new plot that allows users to determine if a small subset of features that is able to well explain the model exists.

Fixes #241

Type of change

• New feature (non-breaking change which adds functionality or feature that would cause existing functionality to not work as expected)

How Has This Been Tested?

Methods used to calculate the metrics have been tested via the pytest module. Those tests are located in tests/unit_tests/utils/test_explanation_metrics.py, tests/unit_tests/explainer/test_smart_explainer.py, tests/unit_tests/explainer/test_smart_plotter.py. In addition, a visualization through the existing tutorial plot has been done.

Test Configuration:

• OS: macOS
• Python version: 3.7
• Shapash version: 1.4.4

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[yg79]

Good job Francesco !
I suggest you some minor modifications