Help in Custom JavaScript Display and Grading Problem

I am trying to implement custom javascript problem. I have my javascript application.
But when I submit my problem it shows “Could not grade your answer. The submission was aborted.”
Here code
let func = (function() {
function showQue() {
let checkBox = document.getElementById(“checkBox”);
let text = document.getElementById(“question”);
if (checkBox.checked == true){ = “block”;
} else { = “none”;

      function getGrade() {
          return "correct"

      return {
          showQue: showQue,
          getGrade: getGrade

and the problem “cms-modules.2b7ffc378730.js:175 Uncaught TypeError: Cannot read property ‘getGrade’ of undefined”. Not sure what I am missing.