Hi @dfangish, here is the list of ONNX-supported ATen operators: ONNX supported TorchScript operators — PyTorch 2.0 documentation
Searching this page for _nested_tensor_from_mask shows that it is not supported yet (same for _transformer_encoder_layer_fwd which would also be needed).
They provide a small guide if you would like to add support for these operators: torch.onnx — PyTorch 2.0 documentation