private ImmutableList<Tag> sortedImmutableTags(Iterable<Tag> tags) {
        requireNonNull(tags, "tags");
        if (tags instanceof Collection && ((Collection<?>) tags).isEmpty()) {
            return this.tags;
        }

        final List<Tag> list = new ArrayList<>(this.tags);
        tags.forEach(list::add);
        return sort(list);
    }
Returns the {@link Tag}s concatenated by the specified {@code tags}.
core/src/main/java/com/linecorp/armeria/common/metric/MeterIdPrefix.java