PYTHON-5168 Add comments

Author: ShaneHarvey

pymongo/logger.py

@@ -97,8 +97,10 @@ class _SDAMStatusMessage(str, enum.Enum):
 
 
 def _log_client_error() -> None:
+    # This is called from a daemon thread so check for None to account for interpreter shutdown.
     logger = _CLIENT_LOGGER
     if logger:
+        # logger.exception includes the full traceback.
         logger.exception("MongoClient background task encountered an error:")