Can I use modAL with estimators from other libraries than scikit-learn like xgboost? #161

Hi there,

I have already trained some good working estimators (xgboost, catboost & lightgbm).
I would like to add an active learner, because we need to decide which data to label continuously.

The documentation says, that I need to use a scikit-learn estimator object. Does that mean I can't use the models from xgboost, catboost & lightgbm? I used the models from the libraries with the same names.

And another question (for my understanding). Do I give an estimator that is already trained, or does the active learner train a model from scratch?

I am new to the field of active learning, so thank you very much!