Cannot run a custom container using smdistributed/dataparallel unless USE_SMDEBUG is turned off

After countless hours of trying to get an `Estimator()` to run on a custom `image_uri` in smdistributed/dataparllel mode (it was failing on trying to import any non-sagemaker-DLC library), I finally discovered buried in the sagemaker.huggingface.HuggingFace estimator that in its API req to sagemaker, it adds the env var

`"USE_SMDEBUG": "0"`

I added this to my custom docker container and suddenly everything worked. Imports from custom libraries worked no problem.

Is this documented anywhere?