Okay so the way it works is that it moves all the logging to background process, But if you have a Lot of data, actually pushing the data between python processes is Not very efficient. This line basically tells it to just use background thread (instead of background process), for sending the data to the server.
The idea behind using background process in the first place is to better support pytorch workers that spin a lot of subprocesses, and we do not want to add a thread per process and increase the time for it takes to spin them