This is strictly debugging and, as the comment indicates, quite likely most of the usage is inside facebook. If you set the environment variable
PYTORCH_API_USAGE_STDERR=1

you can see that PyTorch records “which parts of PyTorch are involved”, quite likely to give you a rough idea where to look (and whom to have look) if something unexpected happens.
PyTorch has grown quite huge with lots of moving bits and sometimes unexpected interactions, so having a quick idea of how to narrow things down or compare high-level processing flow between versions is a debug help.
Bast regards
Thomas