(Do not merge yet. The code is complete and reviewable but tests in the onnx-fb-universe repo are upcoming.)

Also please fix lint (as the CI is failing). Structure wise looks good (though the circular dependencies are starting to get messy)

Lint still broken.

Note that flake8 on the box your dev'ing on is a special snowflake and doesn't actually apply the correct rules. I often pip install flake8 to get a more sane copy.

any more comments? I think this is ready to ship

thanks @anderspapitto