code: @SuppressWarnings("unchecked")
    public <T extends Serializable> Optional<Statistic<T>> queryStatistic(String fullStatisticName, long sinceMillis) {
      ValueStatistic<T> valueStatistic = (ValueStatistic<T>) statistics.get(fullStatisticName);
      if (valueStatistic == null) {
        return Optional.empty();
      }
      return Optional.of(Statistic.extract(valueStatistic, sinceMillis, timeSource.getAsLong()));
    }
docs: Query a statistic based on the full statistic name. Returns null if not found.