instance reweighting mechanism

[xfen974]

Dear author,

Thanks for sharing your code. We have traced through the reweighting mechanism in the repository(pytorch_transformers). In modeling_bert.py, we found the weighted_loss objective function with the hardcoded weights in the input fever training dataset. Unfortunately, we can not find the instance reweighting mechanism with learnable instance weights in both repositories. Can you kindly point us to the right segment in the code that implements this logic in your repository? Thanks for your help!