* assertNull(getEffectiveTldPlusOne("com"));
   * assertNull(getEffectiveTldPlusOne("localhost"));
   * assertNull(getEffectiveTldPlusOne("mymacbook"));
   * ```
   *
   * @param domain A canonicalized domain. An International Domain Name (IDN) should be punycode
   *     encoded.
   */
  fun getEffectiveTldPlusOne(domain: String): String? {
    // We use UTF-8 in the list so we need to convert to Unicode.