cinder/api-ref/source/v3/samples/group-create-from-src-request.json

{
    "create-from-src": {
        "name": "first_group",
        "description": "first group",
        "group_snapshot_id": "6f519a48-3183-46cf-a32f-41815f813986",
        "source_group_id": None
    }
}