wagtail/wagtail/admin/templates/wagtailadmin/panels/object_list.html

{% load wagtailadmin_tags %}

{% for child, identifier in self.visible_children_with_identifiers %}
    {% panel id_prefix=self.prefix id=identifier class_name=child.classes|join:' ' heading=child.heading heading_size="label" icon=child.icon id_for_label=child.id_for_label is_required=child.is_required %}
        {% component child %}
    {% endpanel %}
{% endfor %}