docs: @UiThread
      public void notifyParentDataSetChanged(boolean preserveExpansionState) {
          if (preserveExpansionState) {
              mFlatItemList = generateFlattenedParentChildList(mParentList, mExpansionStateMap);
          } else {
              mFlatItemList = generateFlattenedParentChildList(mParentList);
          }
          notifyDataSetChanged();
      }