chromium/chromeos/components/test/data/onc/third_party_vpn.onc

{
    "GUID": "guid",
    "Name": "third-party VPN",
    "Type": "VPN",
    "VPN": {
        "Type": "ThirdPartyVPN",
        "ThirdPartyVPN": {
            "ExtensionID": "deadbeefdeadbeefdeadbeefdeadbeef",
        }
    }
}