how to assign same value of a key to 2 different keys in output JSON jolt

JavaScript
[
    {
        "operation": "shift",
        "spec": {
            "survey": {
                "key": {
                    "@": [ "a.b.firstProperty", "a.b.secondProperty" ],
                    "#Constant": [ "a.b.thirdProperty", "a.b.fourthProperty" ]
                }
            }
        }
    }
]
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