Drop-in paragraph template to display fields as bootstrap accordian

paragraph--PARA-NAME.html.twig

{% extends "paragraph.html.twig" %}
{% block paragraph %}
  <div{{ attributes.addClass('panel-group') }} id="accordion-{{ paragraph.id() }}" role="tablist">
    {% for field in content %}
      {% set field_instance_items = [] %}
      {% for key, field_instance in field if key|first != '#' %}
        {% set field_instance_items = field_instance_items|merge([field_instance]) %}
      {% endfor %}

      {% if field_instance_items is not empty %}
        <div class="panel panel-default">
          <div class="panel-heading" data-toggle="collapse"
            data-parent="#accordion-{{ paragraph.id() }}" data-target="#collapse{{ loop.index }}">
            
            <h4 class="panel-title">
              <a>
                {{ field['#title'] }}
              </a>
            </h4>
          </div>
          <div id="collapse{{ loop.index }}" class="panel-collapse collapse">
            <div class="panel-body">
              {{ field_instance_items }}
            </div>
          </div>
        </div>
      {% endif %}
    {% endfor %}
  </div>
{% endblock paragraph %}

Note id="accordion-{{ paragraph.id() }}" because potentially multiple per-page.

Attribution:
For getting renderable field values out of {{ content }} @ http://drupal.stackexchange.com/a/208765/160
NB note about compatibility of collapse elements @ http://stackoverflow.com/questions/19236717/how-to-make-a-bootstrap-accordion-collapse-when-clicking-the-header-div
And of course, https://www.w3schools.com/bootstrap/bootstrap_collapse.asp