Import/Export to Onnx in Pytorch vs Caffe2

The code that Imports/Exports a model into ONNX is a separate package for Caffe2 and is part of the ONNX project -

Whereas for PyTorch the import/export functionality ships as part of the PyTorch package itself.

Any reason for this difference? Were there any design decisions or tradeoff involved while making this call?

As for import/export issue, I understand current support functionality for PyTorch and Caffe2.

Is there any issue related to “import ONNX model to PyTorch” in PyTorch issue?