def check_for_ordered(self, op):
        if not self.ordered:
            raise TypeError("Categorical is not ordered for operation {op}\n"
                            "you can use .as_ordered() to change the "
                            "Categorical to an ordered one\n".format(op=op))
Get singleton object from DB
dataset/ETHPy150Open pydata/pandas/pandas/core/categorical.py/Categorical.check_for_ordered--crossover with--dataset/ETHPy150Open openstack/fuel-web/nailgun/nailgun/api/v1/handlers/base.py/DBSingletonHandler.GET