Fix multitarget stratification

[DRMPN]

This is a 🐛 bug fix.

Summary

Disable multitarget stratification when classes are unbalanced.
Add test for this specific scenario.

Context

Fixes #1307

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[pep8speaks]

Hello @DRMPN! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2024-07-02 08:45:21 UTC

[github-actions]

All PEP8 errors has been fixed, thanks ❤️

Comment last updated at

[DRMPN]

Метод внутри пакета sklearn в train_test_split() выполняет one hot encode и превращает изначальные 7 классов в 11:

Вследствие появления "новых" классов, их количества не хватает для стратификации, из-за чего появляется ошибка. Предлагаю превентивно производить проверку и отключать стратификацию.

[DRMPN]

/fix-pep8

[Lopa10ko]

выглядит валидно, если действительно спасает от ошибки деления со стратификацией, как показано на скрине.

[Lopa10ko]

/fix-pep8