signature is not always object. It is valid JOSN type

 select RAW d  FROM default AS d LIMIT 1;

{

    "requestID": "5ec9e832-360a-43f4-8985-a156a15a06c1",

    "signature": "json",

    "results": []

}

SELECT RAW 1;

{

    "requestID": "4fb57d87-5392-4f1b-b135-37e5aeff5cb8",

    "signature": "number",

    "results": [

    1

    ]

}

 select  d  FROM default AS d LIMIT 1;

{

    "requestID": "0d5037ac-4b9c-45ab-bae6-6f6c2e7a1505",

    "signature": {

        "d": "json"

    },

    "results": [

    {

        "d": {

            "color": "green",

            "productId": "97ca4125-2d86-444c-9aba-4c4d2cae5090",

            "type": "product",

            "unitPrice": 4.4

        }

    }

    ],

    "status": "success",

    "metrics": {

        "elapsedTime": "1.696066ms",

        "executionTime": "1.619417ms",

        "resultCount": 1,

        "resultSize": 187

    }

}