default MediaTypeResolver orElse(MediaTypeResolver other) {
        requireNonNull(other, "other");
        if (this == other) {
            return this;
        }
        return (path, contentEncoding) -> {
            final MediaType mediaType = guessFromPath(path, contentEncoding);
            if (mediaType != null) {
                return mediaType;
            }
            return other.guessFromPath(path, contentEncoding);
        };
    }
Returns a newly created {@link MediaTypeResolver} that tries this {@link MediaTypeResolver} first and
then the specified {@code other} when the first call returns {@code null}.
core/src/main/java/com/linecorp/armeria/server/file/MediaTypeResolver.java