def _check_default_subnetpool_exists(self, context, ip_version):
        if self.get_default_subnetpool(context, ip_version):
            msg = _("A default subnetpool for this IP family has already "
                    "been set. Only one default may exist per IP family")
            raise exc.InvalidInput(error_message=msg)
Check if a default already exists for the given IP version.
dataset/ETHPy150Open openstack/neutron/neutron/db/db_base_plugin_v2.py/NeutronDbPluginV2._check_default_subnetpool_exists