docs: public static MetricName join(MetricName... parts) {
          final StringBuilder nameBuilder = new StringBuilder();
          final Map<String, String> tags = new HashMap<>();
  
          boolean first = true;
  
          for (MetricName part : parts) {
              final String name = part.getKey();
  
              if (name != null && !name.isEmpty()) {
                  if (first) {
                      first = false;
                  } else {
                      nameBuilder.append(SEPARATOR);
                  }
  
                  nameBuilder.append(name);
              }
  
              if (!part.getTags().isEmpty())
                  tags.putAll(part.getTags());
          }
  
          return new MetricName(nameBuilder.toString(), tags);
      }