{# Simple form with default templates: {{ upper({href: str, label: str, children: link[]}) }} Advanced form with custom templates: {% call(part, details) upper(upper_groups) %} {% if part == "heading" %} HEADING: {{ details.label }} {% elif part == "link" %} LINK: {{ details.label }} {% endif %} {% endcall %} #} {% macro upper(groups) %} {% endmacro %}