Init feature to_smartexplainer

[johannmartin95]

Description

Add a new method on SmartPredictor object "to_smartexplainer" to switch from a SmartPredictor Object to a SmartExpxlainer one.

• Start with a check to ensure that the add_input step has been done with the SmartPredictor to get the specific data on which we want to analyse several charts
• Check if preprocessing isn't a ColumnTransformer, otherwise raise ValueError
• Initialize SmartExplainer Object with attributes from SmartPredictor
• Compute the compile step of SmartExplainer with attributes and input used by the SmartPredictor for parameters

Fixes #111

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?

• Unit test added on test_smart_predictor.py

Test Configuration:

• OS: Linux
• Python version: 3.6/3.7/3.8
• Shapash version: 1.2.0

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 Johann