API client_get -> sites_web_domain_get

For invoicing I try to get the hosting information via de API. I now the client_ids but I don't know what client has what domain. I the database I found the relation table sys_group. But how can I do that via the API?

With client_get_all I can get all the client_ids, with client_get(client_id), I can get the specific client information.
With the client_id I can get the related groupid and with the groupid I can get the related domain_ids. And with sites_web_domain_get(domain_id) I have the domain information.
In the database the relation between client and site is linked via the table sys_group. But how can I find this relation via the API?

 

If I do a
{"session_id": "fadba2d5d0edea01665d6ecc87df5d0c", "primary_id": {"client_id": "1"}} to the REST API on ispconfig.local:8080/remote/json.php?sites_web_domain_get I get {"code":"ok","message":"","response":[]}

So probably I don't use the correct function. What is the function that I need to use to get the group_id?

 

After multiple times searching, I found client_get_groupid. I think this does the trick.

 

Thanks so much M. Piscaer.
That's the function that I was looking for.