{% macro avatar_stack(agents) -%}
{% if agents -%}
<span class="avatar-stack">
{%- for a in agents -%}
<span class="avatar-initials" data-hue="{{ a | avatar_hue }}" title="{{ a }}">{{ a | initials }}</span>
{%- endfor -%}
</span>
{%- endif %}
{%- endmacro %}