postman pre-request script (post raw2)

pm.sendRequest({
    url: "<host>/api/sign_in",
    method: 'POST',
    header: 'Content-Type:application/json',
    body: {
        mode: 'raw',
        raw: JSON.stringify({
            "email": pm.environment.get("user_email"),
            "password": pm.environment.get("user_password")
          })
        }
}, function (err, response) {
    if (response) {
      pm.environment.set("access_token_header", response.headers.get('access-token'));
      pm.environment.set("client_header", response.headers.get('client'));
      pm.environment.set("expiry_header", response.headers.get('expiry'));
      pm.environment.set("uid_header", response.headers.get('uid'));
    }
});