docs: private Set<String> getCSSHeadIncludes(CmsObject cms, CmsResource resource) {
  
          if (CmsResourceTypeXmlContent.isXmlContent(resource)) {
              try {
                  CmsXmlContentDefinition contentDefinition = CmsXmlContentDefinition.getContentDefinitionForResource(
                      cms,
                      resource);
                  return contentDefinition.getContentHandler().getCSSHeadIncludes(cms, resource);
              } catch (CmsException e) {
                  LOG.warn(e.getLocalizedMessage(), e);
                  // NOOP, use the empty set
              }
          }
          return Collections.emptySet();
      }