Add Apex import Guard for MM collection
> Please capture the error and include in the ImportError so users will know exactly what's not being imported properly.

ImportError is raised at the model level not layer level. Most of the cases here are using Apex's `groupnorm`, I added the ImportError when instantiate the model, not for each layer we invoke groupnorm.

@ericharper do you think this is sufficient ? This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. This PR was closed because it has been inactive for 7 days since being marked as stale.