private static String normalizeToken(String token) {
        checkArgument(TOKEN_MATCHER.matchesAllOf(token));
        checkArgument(!token.isEmpty());
        return Ascii.toLowerCase(token);
    }
Creates a media type with the "video" type and the given subtype.

@throws IllegalArgumentException if subtype is invalid
core/src/main/java/com/linecorp/armeria/common/MediaType.java