Sort init import (#10801)

* Initial script

* Add script to properly sort imports in init.

* Add to the CI

* Update utils/custom_init_isort.py

Co-authored-by: Lysandre Debut <lysandre@huggingface.co>

* Separate scripts that change content from quality

* Move class_mapping_update to style_checks

Co-authored-by: Lysandre Debut <lysandre@huggingface.co>

.circleci/config.yml

@@ -383,6 +383,7 @@ jobs:
                       - '~/.cache/pip'
             - run: black --check examples tests src utils
             - run: isort --check-only examples tests src utils
+            - run: python utils/custom_init_isort.py --check_only
             - run: flake8 examples tests src utils
             - run: python utils/style_doc.py src/transformers docs/source --max_len 119 --check_only
             - run: python utils/check_copies.py