static MediaType createVideoType(String subtype) {
    return create(VIDEO_TYPE, subtype);
  }

  private static String normalizeToken(String token) {
    checkArgument(TOKEN_MATCHER.matchesAllOf(token));
    checkArgument(!token.isEmpty());
    return Ascii.toLowerCase(token);
  }

  private static String normalizeParameterValue(String attribute, String value) {
    checkNotNull(value); // for GWT