test1/public/drupal/core/modules/system/templates/region.html....

{#
/**
 * @file
 * Default theme implementation to display a region.
 *
 * Available variables:
 * - content: The content for this region, typically blocks.
 * - attributes: HTML attributes for the region <div>.
 * - region: The name of the region variable as defined in the theme's
 *   .info.yml file.
 *
 * @see template_preprocess_region()
 *
 * @ingroup themeable
 */
#}
{% if content %}
  <div{{ attributes }}>
    {{ content }}
  </div>
{% endif %}