Dict is a reference type (#20669)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20669
Before, Dict was a value type, i.e. copying it did a deep copy.
Unfortunately, this doesn't work well with storing and passing Dicts around in IValues because IValues are reference types.
This diff changes Dict to be a reference type.
Reviewed By: dzhulgakov
Differential Revision: D15404911
fbshipit-source-id: dc990d3eb7cae044b74dd0253f8b704dde6a6c86
