* [Improve] Speed up data preprocessor.
* Add ClsDataSample serialization override functions.
* Add unit tests
* Modify configs to fit new mixup args.
* Fix `num_classes` of the ImageNet-21k config.
* Update docs.
* [Refactor] Use mdformat instead of markdownlint to format markdown.
* Update unavailiable api links in tutorials
* Update CONTRIBUTING.md
* Use mdformat==0.7.9 to support Python 3.6
* Add cosine cool down lr updater
* Use ema hook
* Update decay mult
* Update configs.
* Update T2T-ViT readme and format all readme
* Update swin readme
* Update tnt readme
* Add docstring for `CosineAnnealingCooldownLrUpdaterHook`.
* Update t2t readme and metafile
* Fix MobileNet V3 configs
* Refactor to support more powerful feature extraction.
* Add unit tests
* Fix unit test
* Imporve according to comments
* Update checkpoints path
* Fix unit tests
* Add docstring of `simple_test`
* Add docstring of `extract_feat`
* Update model zoo
* Support DeiT backbone.
* Use hook to automatically resize pos embed
* Update ViT training setting
* Add deit configs and update docs
* Fix vit arch assertion
* Remove useless init function
* Add unit tests.
* Fix resize_pos_embed for DeiT
* Improve according to comments.