add some comment

torch_xla/__init__.py

@@ -158,7 +158,7 @@ def _prepare_to_exit():
     # Due to https://bugs.python.org/issue27035, simply raising an exception in the atexit callback does not set the exit code correctly. That is why we need to set the exit code explicitly.
     # Using `exit(1)` does not set a correct exit code because it is useful for the interactive interpreter shell and should not be used in programs and it works by raising an exception. (https://docs.python.org/3/library/constants.html#exit)
     # sys.exit(1) does not set a correct exit code because it also raises an exception.
-    exit(1)
+    os._exit(1)
 
 
 def _init_xla_lazy_backend():