drupal/core/modules/rdf/templates/rdf-metadata.html.twig

{#
/**
 * @file
 * Default theme implementation for empty spans with RDF attributes.
 *
 * Available variables:
 * - metadata: Each item within corresponds to its own set of attributes,
 *   and therefore, needs its own 'attributes' element.
 *
 * @see template_preprocess_rdf_metadata()
 *
 * @ingroup themeable
 */
#}
{% for attributes in metadata %}
  <span{{ attributes.addClass('rdf-meta', 'hidden') }}></span>
{% endfor %}