docs: @Override
      public void onRangeChange(int start, int end) {
          if (end - start < 4) {
              throw new IllegalArgumentException(
                      "pls use OnePlusNLayoutHelper instead of OnePlusNLayoutHelperEx which childcount <= 5");
          }
          if (end - start > 6) {
              throw new IllegalArgumentException(
                      "OnePlusNLayoutHelper only supports maximum 7 children now");
          }
      }