docs: public SafeHtml toSafeHtml() {
      Preconditions.checkState(
          getContentKind() == ContentKind.HTML,
          "toSafeHtml() only valid for SanitizedContent of kind HTML, is: %s",
          getContentKind());
      return UncheckedConversions.safeHtmlFromStringKnownToSatisfyTypeContract(getContent());
    }