def callback(self, result):
        assert not isinstance(result, Deferred)
        self._startRunCallbacks(result)
Gets a single bucket listing reference for an acl get command.
dataset/ETHPy150Open twisted/twisted/twisted/internet/defer.py/Deferred.callback--crossover with--dataset/ETHPy150Open GoogleCloudPlatform/gsutil/gslib/command.py/Command.GetAclCommandBucketListingReference