old_contents: module.exports = {
    deepCopy: function(obj){
      return JSON.parse(JSON.stringify(obj));
    }
  };
  
new_contents: module.exports = {
    deepCopy: function(obj){
      if (obj === null || obj === undefined) {
        return obj;
      }
      return JSON.parse(JSON.stringify(obj));
    }
  };
  
subject: fix utils#deepCopy