Naming

[kegl]

Consider renaming train_is to train_idxs and labels to label_names.

[aboucaud]

I guess you meant train_is to train_ids or train_idx

[glemaitre]

Since that there is couple of occurences with idxs in scikit-learn, I would agree with it :D

https://github.com/scikit-learn/scikit-learn/search?utf8=%E2%9C%93&q=idxs&type=

[jorisvandenbossche]

But most of the time sklearn uses either just train, test = cv.splilt(..) or train_index, test_index = cv.split(..)