I managed to get https://www.drupal.org/project/paragraphs_jquery_ui_accordion working in Backdrop last week but I really want Bootstrap Accordions.  I've found the Field Collection template file in the Drupal code.  How do you do this with Paragraphs?  

<div class="panel-group" id="accordion" role="tablist" aria-multiselectable="true">

  <?php foreach($rows as $key => $row) { ?> 

    <div class="panel panel-default">

        <div class="panel-heading" role="tab" id="heading-<?php print $key . '-' . $row['entity_id']; ?>">

            <h4 class="panel-title">

                <a role="button" data-toggle="collapse" data-parent="#accordion" href="#collapse-<?php print $key . '-' . $row['entity_id']; ?>" aria-expanded="true" aria-controls="collapse-<?php print $key . '-' . $row['entity_id']; ?>">

                     <?php print $row['field_fc_title']; ?>

                </a>

            </h4>

        </div>

        <div id="collapse-<?php print $key . '-' . $row['entity_id']; ?>" class="panel-collapse collapse" role="tabpanel" aria-labelledby="heading-<?php print $key . '-' . $row['entity_id']; ?>">

            <div class="panel-body">

                <?php print $row['field_fc_panel_body']['value']; ?>

            </div>

        </div>

    </div>

  <?php } ?>

</div>