GitLab

Summary:
Pull Request resolved: https://github.com/facebookresearch/d2go/pull/349

This is to allow None, meaning model_configs is not used.

Added tasks for the other TODO.

Reviewed By: wat3rBro

Differential Revision: D38199075

fbshipit-source-id: 774ca42a82a972b7e4c642cc4306aec39e2c2f7f