我正在使用bootstrap显示多选下拉菜单，但它显示的是简单下拉菜单

<div class="dropdown">
  <button class="btn btn-secondary dropdown-toggle" type="button" id="dropdownMenuButton" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
    选择
  </button>
  <div class="dropdown-menu" aria-labelledby="dropdownMenuButton">
    <!-- 菜单项 -->
  </div>
</div>

<div class="dropdown-menu" aria-labelledby="dropdownMenuButton">
  <label class="dropdown-item">
    <input type="checkbox" value="option1"> 选项1
  </label>
  <label class="dropdown-item">
    <input type="checkbox" value="option2"> 选项2
  </label>
  <!-- 其他菜单项 -->
</div>

$('.dropdown-menu').on('click', function(e) {
  if ($(this).hasClass('dropdown-menu-form')) {
    e.stopPropagation();
  }
});