PyTorch model metadata. (#16275)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16275
Adding a generic string `metadata` field as part of the model to capture additional metadata with the model.
Reviewed By: dzhulgakov
Differential Revision: D13579029
fbshipit-source-id: 7456ef2edbe73bb70bbb31889cecd94e0db329a2
