Fix non-nesting bug in BetterTransformer integration (#637)
* small patch
* fix all models
* add test
* fix import
* import bis
* more tests
* fix bug
* informative log
* fix test
* add reason
* remove print
* better test
* fix log
Co-authored-by: Felix Marty <9808326+fxmarty@users.noreply.github.com>
