code: function (checkListContent) {
      var prefix;
      if (isNumberedList) {
        prefix = " " + num + ". ";
        num++;
      } else {
        prefix = " " + bullet + " ";
        if (isCheckList) {
          prefix += '[';
          prefix += checkListContent || ' ';
          prefix += '] ';
        }
      }
      return prefix;
    }
docs: Get the item prefix - e.g. " 1. " for a numbered list, " - " for a bulleted list.