How do you keep multiple collapses open in Bootstrap 3?

Update 2020

Bootstrap 4

How do you make Twitter Bootstrap Accordion keep one group open?

Bootstrap 3

You can just remove the data-parent attribute that is normally used in the accordion markup.

<div class="panel-group" id="accordion">
  <div class="panel panel-default">
    <div class="panel-heading">
      <h4 class="panel-title">
        <a class="accordion-toggle" data-toggle="collapse" href="#collapseOne">
          Collapsible Group Item #1
        </a>
      </h4>
    </div>
     ... 

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