code: public static <Item extends IItem & IExpandable> void notifyItemsChanged(final FastAdapter adapter, ExpandableExtension expandableExtension, Set<Long> identifiers, boolean restoreExpandedState) {
          int i;
          IItem item;
          for (i = 0; i < adapter.getItemCount(); i++) {
              item = adapter.getItem(i);
              if (item instanceof IExpandable) {
                  notifyItemsChanged(adapter, expandableExtension, (Item) item, identifiers, true, restoreExpandedState);
              } else if (identifiers.contains(item.getIdentifier())) {
                  adapter.notifyAdapterItemChanged(i);
              }
          }
      }
docs: notifies items (incl. sub items if they are currently extended)
  
  @param adapter              the adapter
  @param identifiers          set of identifiers that should be notified
  @param restoreExpandedState true, if expanded headers should stay expanded