Adds a guide for using the as_numpy argument in fit, cv and preprocess.
Also improves the custom training guide for the case when some models should be trained normally and others in a custom way.
Checklist:
[x] This PR has a meaningful title and a clear description.
Description
Adds a guide for using the
as_numpy
argument in fit, cv and preprocess. Also improves the custom training guide for the case when some models should be trained normally and others in a custom way.Checklist: