I am using this markup for a Boostrap accordion/collapsible panel. How can I have ALL my sections open on page load instead of collapsed?

```
<div class="panel-group" id="accordion" role="tablist" aria-multiselectable="true">
    <div class="panel panel-default">
        <div class="panel-heading" role="tab" id="headingOne">
            <h4 class="panel-title">
                <a class="collapsed accordion-toggle" role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseOne" aria-expanded="false" aria-controls="collapseOne"> Header </a>
            </h4>
        </div>
        <div id="collapseOne" class="panel-collapse collapse" role="tabpanel" aria-labelledby="headingOne">
            <div class="panel-body">
                collapsible stuff
            </div>
        </div>
    </div>
</div>

```