Jinja2 filter: collapse nested dictionary into HTML table

collapser.html

{% macro render_nested(json, key) -%}
<table>
  {% if json.get(key) %}
    {% for key, value in json.get(key).items() recursive %}
      {% if value is mapping %}
        {{ loop(value.items()) }}
      {% else %}
        <tr>
          <td>{{ key }}</td> 
          <td>{{ value }}</td>
        </tr>
      {% endif %}
    {% endfor %}
  {% else %}
    <p>None</p>
  {% endif %}
</table>
{%- endmacro %}