- def checkCredentials(self, creds, operation, xrns=[], check_sliver_callback=None, speaking_for_hrn=None):
-
+ # do not use mutable as default argument
+ # http://docs.python-guide.org/en/latest/writing/gotchas/#mutable-default-arguments
+ def checkCredentials(self, creds, operation, xrns=None,
+ check_sliver_callback=None, speaking_for_hrn=None):
+ if xrns is None: xrns=[]