code: protected final T getDefaultStats(OnDemandStatsProducer producer) {
          try {
              return getStatsClass().cast(producer.getDefaultStats());
          } catch (ClassCastException e) {
              LOGGER.error("getDefaultStats(): Unexpected stats type", e);
              return null;
          }
      }
docs: Returns default stats for producer.
  
  @param producer {@link OnDemandStatsProducer}
  @return default stats for producer