>
                {% firstof icon "placeholder" as icon_name %}
                {% icon name=icon_name classname="w-panel__icon" %}
            </button>
            {% if heading %}
                <h2 class="w-panel__heading {% if heading_size == "label" %}w-panel__heading--label{% endif %}" {% if heading_level %}aria-level="{{ heading_level }}"{% endif %} id="{{ heading_id }}" data-panel-heading>
                    {% if id_for_label %}
                        <label for="{{ id_for_label }}" id="{{ id_f