djLint/tests/source_django/select.html

<select name="{{ widget.name }}"
        {% include "django/forms/widgets/attrs.html" %}>
    {% for group_name, group_choices, group_index in widget.optgroups %}
        {% if group_name %}<optgroup label="{{ group_name }}">{% endif %}
        {% for option in group_choices %}
            {% include option.template_name with widget=option %}
        {% endfor %}
        {% if group_name %}</optgroup>{% endif %}
    {% endfor %}
</select>