Hydra versions prior to 1.1 supported overriding of Hydra config groups via the Defaults List in this manner:
defaults: - model: resnet50 - hydra/launcher: submitit
As of Hydra 1.1, Config group overrides must be marked explicitly with the
defaults: - model: resnet50 - override hydra/launcher: submitit
The Defaults List is described here.
override keyword when overriding Hydra's config groups will result in an error in Hydra 1.2