docs: public String toRawString(char delimiter)
      {
          StringBuilder result = new StringBuilder();
          for (Entry<String, PerfCounter> e : Counters.entrySet()) {
              result.append(e.getKey())
                    .append(delimiter)
                    .append(e.getValue().toRawString(delimiter))
                    .append('\n');
          }
          return result.toString();
      }