[MRG] Add the option to pass a KNeighborsMixin instead of simple n_neigbors #182
@glemaitre, first at all, good job! This will be useful for techniques that use adaptive distances (such as undersampling methods like ATISA).
Now, if we want to allow a user to pass a NearestNeighbors object, we should allow him to pass a RadiusNeighborsClassifier, and this object doesn't have a
Something like this should do the work:
I am not against it. However, I see an issue coming using metric distance.
I would split this for another PR in which we ensure that the algorithm can handle such specificity.