scikit-learn/scikit-learn — comment on commit 87c8664d1a3b350ab91694f87caaf631e33a6944
File:  line 0
By larsmans:

`decision_function` isn't implemented for sparse SVMs, but in the old inheritance tree, it inherited the one from `BaseLibSVM`. So, `OneVsRestClassifier` detected the dense `decision_function` even for sparse SVMs, which didn't work and raised an exception because of missing `self._support`.

In the new situation, `decision_function` is in `DenseBaseLibSVM` so it's no longer inherited by the sparse SVM classes and `predict_proba` is used instead.