def describe_subnet_groups(self, subnet_group_name):
        if subnet_group_name:
            if subnet_group_name in self.subnet_groups:
                return [self.subnet_groups[subnet_group_name]]
            else:
                raise DBSubnetGroupNotFoundError(subnet_group_name)
        return self.subnet_groups.values()
dataset/ETHPy150Open spulec/moto/moto/rds/models.py/RDSBackend.describe_subnet_groups/original