请教各位,bootstrap已经引入,手风琴效果不显示
<div class="accordion" id="accordion2">
<!--第一组-->
<div class="accordion-group">
<div class="accordion-heading">
<a href="#collapseOne" class="accordion-toggle" data-toggle="collapse" data-parent="#accordion2">
aa
</a>
</div>
<div id="collapseOne" class="accordion-body collapse in">
<ul class="accordion-inner">
<li><a href="">bb</a></li>
</ul>
</div>
</div>
</div>