How to get the request body raw inside test cases in TESTS scripts POSTMAN?

I am trying to get the request body raw inside test cases in TESTS scripts?
Here the script in TESTS:

pm.sendRequest({
        url: pm.collectionVariables.get("url") + '/xxxxx/' + api + '/xxxxxxxxxxx',
        method: 'POST',
        header: {
            'content-type': 'application/json',
            'application': pm.collectionVariables.get("sha256"),
            'sign': pm.collectionVariables.get("sign")
        },
        body: {
            mode: 'raw',
            raw: JSON.stringify({
                deviceId: null,
                email: null
            })
        }
    }, console.log(“Request Body: ”, JSON.parse(pm.request.body.raw)),
    function(err, res) {
        pm.test(“N: All Parameter Null”, function() {
            pm.expect(res).to.have.property(‘code’, 200);
            pm.expect(res.json()).to.have.property(‘status’, ‘00’);
            pm.expect(res.json()).to.have.property(‘message’, ‘Success’);
            console.info("All Parameter Null Response Time: " + res.responseTime)
        });
    })

I’m using console.log(“Request Body :”, JSON.parse(pm.request.body.raw)) to get request body raw, but the content i got is the raw data from BODY (Main Test Cases)

the purpose of this question is to create a signature in the header, based on request body raw that generated with secret key
i have no problem to create signature in BODY (Main Test Cases), the problem only inside TESTS

How can I get the request body from TESTS ?
or anyone experience how to create signature inside TESTS?