docs: public TrustedResourceUrl toTrustedResourceUrl() {
      Preconditions.checkState(
          getContentKind() == ContentKind.TRUSTED_RESOURCE_URI,
          "toTrustedResourceUrl() only valid for SanitizedContent of kind TRUSTED_RESOURCE_URI, "
              + "is: %s",
          getContentKind());
      return UncheckedConversions.trustedResourceUrlFromStringKnownToSatisfyTypeContract(
          getContent());
    }