Allow nested lists/dicts in legacy operator API (#20379)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20379
The legacy custom op API allowed nesting of std::unordered_map and std::vector. While we haven't figured out yet how to do that with the new API,
we at least have to keep backwards compatibility. This diff adds the feature so we can switch to the new API without breaking third party code.
Reviewed By: li-roy
Differential Revision: D15287693
fbshipit-source-id: bb5b8429fddf6298719cbf567b584ed371f8fc81
