Gateway Server API

Hello how do I use the following gateway server api (‘GatewayConfigurationService’) ? /api/v3/gcs/gateways/configuration/{gateway_ids.gateway_id}/{format}/{filename}
I read the documentation there : Gateway Server APIs | The Things Stack for LoRaWAN
but I’m unable to understand what is format and filename (I tried json/global_conf.json) but it didn’t work.