* fix dataset wrapper bug and add unit tests
* fix dataset wrapper bug and add unit tests
* update unit tests
* fix lint
* align interface to mmdet
* update unit tests
* add imagnet21k
* Update unit test
* update imaenet21k
* use slots
* use slots
* rename Data_item to ImageInfo
* add unit tests
* Update unit tests
* rm some print
* update unit tests
* fix lint
* remove default value of pipeline
* Refactor unit tests folder structure.
* Remove label smooth and Vit test in `test_classifiers.py`
* Rename test_utils in dataset to test_dataset_utils
* Split test_models/test_utils/test_utils.py to multiple sub files.
* Add unit tests of classifiers and heads
* Use patch context manager.
* Add unit test of `is_tracing`, and add warning in `is_tracing` if torch
verison is smaller than 1.6.0