multilabelでStratifiedKFold
#iterative-stratification
前提
multilabel（機械学習用語）
https://scikit-learn.org/stable/modules/generated/sklearn.model_selection.StratifiedKFold.html
Sechidis K., Tsoumakas G., Vlahavas I. (2011)
（積ん読）On the Stratification of Multi-Label Data
https://link.springer.com/content/pdf/10.1007/978-3-642-23808-6_10.pdf
で見られるっぽい（Google検索でサジェスト）
from iterstrat.ml_stratifiers import MultilabelStratifiedKFold