How to use getSpaceGroups json-rpc api

I want to get all the space groups assigned to a space. I was using the Atlassian REST API Browser and found the API " json-rpc/confluenceservice-v1/getSpaceGroups" to fetch the groups of a space. I tried using this API to fetch the space groups but got the error “The request body could not be parsed as JSON”. I entered ds in the body, I also tried using [“ds”], “ds” but got no luck. Can anyone please tell me how to use this API?

I know this SOAP API will be removed in the future, but for the time being, I can’t wait for the REST API to arrive, so I’m okay with using this one.