* Add mixup option
* Modify the structure of mixup and add configs
* Clean configs
* Add test for mixup and SoftCrossEntropyLoss
* Add simple test for ImageClassifier
* Fix bug in test_losses.py
* Add assertion in CrossEntropyLoss
* resolve conflicts
add heads and config for multilabel tasks
* minor change
* remove evaluating mAP in head
* add baseline config
* add configs
* reserve only one config
* minor change
* fix minor bug
* minor change
* minor change
* add unittests and fix docstrings