2020-09-02 scikit-learn internal API

The signature of method impurity_improvement will change for version 0.24. That’s usually easy to handle two versions of scikit-learn even overloaded in a class except that method is implemented in cython. The method must be overloaded the same way with the same signature. The way it was handled is implemented in PR 88.

The best would be to include both of them but only one of them can compile. I did not find any good solution to that. It compiles whatever scikit-learn’s version but the compiled module only works with the installed version of :epkg:`scikti-learn`.