docs: @UiThread
      public void notifyParentRangeInserted(int parentPositionStart, int itemCount) {
          int initialFlatParentPosition;
          if (parentPositionStart < mParentList.size() - itemCount) {
              initialFlatParentPosition = getFlatParentPosition(parentPositionStart);
          } else {
              initialFlatParentPosition = mFlatItemList.size();
          }
  
          int sizeChanged = 0;
          int flatParentPosition = initialFlatParentPosition;
          int changed;
          int parentPositionEnd = parentPositionStart + itemCount;
          for (int i = parentPositionStart; i < parentPositionEnd; i++) {
              P parent = mParentList.get(i);
              changed = addParentWrapper(flatParentPosition, parent);
              flatParentPosition += changed;
              sizeChanged += changed;
          }
  
          notifyItemRangeInserted(initialFlatParentPosition, sizeChanged);
      }