docs: public Long getDeleteCountAvg() {
          Long deleteCountAvg = 0L;
          if (items.size() != 0) {
              for (TableStat item : items) {
                  if (item.getEndTime().equals(item.getStartTime())) {
                      deleteCountAvg += item.getDeleteCount();
                  } else {
                      deleteCountAvg += item.getDeleteCount() * 1000
                                        / (item.getEndTime().getTime() - item.getStartTime().getTime());
                  }
              }
              deleteCountAvg = deleteCountAvg / items.size();
          }
          return deleteCountAvg;
      }