{#- An <img> that uses the WebP previews from tools/docs_thumbnails.py when they
    match the source image, and the full-size image otherwise. -#}
{% macro preview(image, sizes, attrs='') -%}
{%- set thumb = docs_thumbs.get(image) -%}
{%- if thumb -%}
<img src="{{ (thumb.files|last).path|url }}" srcset="{% for file in thumb.files %}{{ file.path|url }} {{ file.width }}w{% if not loop.last %}, {% endif %}{% endfor %}" sizes="{{ sizes }}" {{ attrs }}>
{%- else -%}
<img src="{{ image|url }}" {{ attrs }}>
{%- endif -%}
{%- endmacro %}