Training benchmark failed with valid_subsets referenced before assignment error

Created by: roywei

🐛 Bug

When I test training code and enabled benchmarking, it will throw valid_subsets referenced before assignment error

To Reproduce

Command:

opt-baselines -n 1 -g 8 -p test_v0 --model-size 125m --aws --benchmark --checkpoints-dir /fsx/metaseq_models/ --no-save-dir

Error:

4:     hyperparam("--valid-subset", ",".join(f"valid/{ss}" for ss in valid_subsets)),
4: UnboundLocalError
4: : local variable 'valid_subsets' referenced before assignment

raised a fix: https://github.com/facebookresearch/metaseq/pull/286