@Override
    public String toString() {
        if (tags.isEmpty()) {
            return name;
        }

        final StringBuilder buf = new StringBuilder();
        buf.append(name).append('{');
        tags.forEach(tag -> buf.append(tag.getKey()).append('=')
                               .append(tag.getValue()).append(','));
        buf.setCharAt(buf.length() - 1, '}');
        return buf.toString();
    }
Returns a newly-created instance whose name is concatenated by the specified {@code tags}.
core/src/main/java/com/linecorp/armeria/common/metric/MeterIdPrefix.java