Why do not use 'torch.nn.MultiheadAttention' to substitude 'Class BertSelfAttention+BertSelfOutput' for pytorch
# 📚 Migration

## Information
pytorch has 'torch.nn.MultiheadAttention' 
https://pytorch.org/docs/1.3.0/nn.html?highlight=multihead#torch.nn.MultiheadAttention

## Details
1. For Better performace and generality, I suggest to use  'torch.nn.MultiheadAttention'  instead of 'Class BertSelfAttention+BertSelfOutput'  in BERT model




'BertSelfAttention+BertSelfOutput'   is tensorflow style
'torch.nn.MultiheadAttention' is real pytorch style<|||||>This issue has been automatically marked as stale and been closed because it has not had recent activity. Thank you for your contributions.

If you think this still needs to be addressed please comment on this thread.<|||||>The layers from the Pytorch will be significantly faster than using the two classes like in TensorFlow. Can't we make an exception for pytorch to use the optimized layers?