@classmethod
    def _iterable_order_by(cls, iterable, order_by):
        order_by_fields = []
        for field_name in order_by:
            if field_name.startswith('-'):
                order_by_fields.append({'name': field_name.lstrip('-'),
                                        'lt': 1, 'gt': -1})
            else:
                order_by_fields.append({'name': field_name,
                                        'lt': -1, 'gt': 1})
        # 'cmp' argument for 'sorted' function is removed in python3.
        # Next code should work fine for both python2 and python3
        key = functools.cmp_to_key(functools.partial(cls.single.compare,
                                                     order_by=order_by_fields))
        return sorted(iterable, key=key)
Fail unless the ``RPM`` file at ``rpm_path`` contains all the
dataset/ETHPy150Open openstack/fuel-web/nailgun/nailgun/objects/base.py/NailgunCollection._iterable_order_by--crossover with--dataset/ETHPy150Open ClusterHQ/flocker/admin/test/test_packaging.py/assert_rpm_headers