def _get_datetime_range(self, req):
        qs = req.environ.get('QUERY_STRING', '')
        env = urlparse.parse_qs(qs)
        # NOTE(lzyeval): env.get() always returns a list
        period_start = self._parse_datetime(env.get('start', [None])[0])
        period_stop = self._parse_datetime(env.get('end', [None])[0])

        if not period_stop < period_start:
            msg = _("Invalid start time. The start time cannot occur after "
                    "the end time.")
            raise exc.HTTPBadRequest(explanation=msg)

        detailed = env.get('detailed', ['0'])[0] == '1'
        return (period_start, period_stop, detailed)
dataset/ETHPy150Open BU-NU-CLOUD-SP16/Trusted-Platform-Module-nova/nova/api/openstack/compute/simple_tenant_usage.py/SimpleTenantUsageController._get_datetime_range/swapped operands of `<`