Resolve L2SS-770 "Fix pyflakes linting errors"

Closes L2SS-770

tangostationcontrol/tangostationcontrol/clients/opcua_client.py

@@ -9,7 +9,7 @@ from tangostationcontrol.clients.comms_client import AsyncCommClient
 import logging
 logger = logging.getLogger()
 
-__all__ = ["OPCUAConnection", "event_loop"]
+__all__ = ["OPCUAConnection", "ProtocolAttribute"]
 
 numpy_to_OPCua_dict = {
     numpy.bool_: asyncua.ua.VariantType.Boolean,