code: public String humanTime(final Stat name) {
          name.requiresTimer();
          Preconditions.checkState(name.isTimer(), "Stat %s is not timer stat", name);
          final Stopwatch stopwatch = tracker.getTimers().get(name);
          return stopwatch == null ? "0" : stopwatch.toString();
      }
docs: Value is reported in best suited units (e.g. milliseconds, seconds, minutes etc).
  
  @param name statistic name
  @return human readable (formatted) timer value or 0 (if stat value is not available)
  @throws IllegalStateException if provided stat is not time stat