code: public void notifyParentRangeRemoved(int parentPositionStart, int itemCount) {
          int sizeChanged = 0;
          int flatParentPositionStart = getFlatParentPosition(parentPositionStart);
          for (int i = 0; i < itemCount; i++) {
              sizeChanged += removeParentWrapper(flatParentPositionStart);
          }
  
          notifyItemRangeRemoved(flatParentPositionStart, sizeChanged);
      }
docs: Notify any registered observers that the {@code itemCount} parents previously
  located at {@code parentPositionStart} have been removed from the data set. The parents
  previously located at and after {@code parentPositionStart + itemCount} may now be
  found at {@code oldPosition - itemCount}.
  <p>
  This is a structural change event. Representations of other existing items in the
  data set are still considered up to date and will not be rebound, though their positions
  may be altered.
  
  @param parentPositionStart The previous position of the first parent that was
  removed, relative to list of parents only.
  @param itemCount Number of parents removed from the data set