Adding decision tree explainers

[zyteka]

This task description is still in progress

Task Summary

This task will involve adding a new DecisionTreeExplainer class of objects, with one algorithm implementation. DecisionTreeExplainer objects explain by 1) decomposing arbitrary models into decision trees and 2) visualizing the decision rules associated with a prediction.

Tasks For Completion

The DecisionTreeExplainer class should follow the same pattern as the existing GlobalFeatureImportance and LocalFeatureContribution classes. This will include the following tasks:

• [x] Create a new dte directory under pyreal/explainers/
• [x] Create a new dte/base.py file, which defines the abstract class DecisionTreeExplainerBase(Explainer, ABC). This class should define fit and produce functions, which will include any code common to all DecisionTreeExplainer objects. They may either be abstract (if no such common code exists) or call an abstract helper function. See gfi and lfc for examples.
• [x] Create a new dte/decision_tree_explainer.py file that defines a class called DecisionTreeExplainer(DecisionTreeExplainerBase). This class will generate a decision tree explanation with its produce function by offloading computation to an implementation class. The implementation class is chosen by a choose_algorithm function, which currently will always return surrogate_tree
• [x] dte/decision_tree_explainer will also have a dte function that allows users to get a DecisionTreeExplainer without creating an object, by internally creating, fitting, and calling produce on a DecisionTreeExplainer
• [x] Create a new dte/surrogate_decision_tree.py that defines a SurrogateDecisionTree(DecisionTreeExplainerBase) class. The produce function on this class should return a decision tree model, trained on the outputs of the original model on a training set.
• [x] Add units tests for all new functionality
• [x] Add documentation for all new functionality

[wei-enwang]

I think we should specify if the model is dealing with a classification or regression problem. They have different decision tree models/

[wei-enwang]

Issue complete

[wei-enwang]

Ready to merge