code: public Set<Item> getSelectedItems() {
          if (mOriginalItems != null) {
              Set<Item> selections = new HashSet<>();
              for (int i = 0, size = mOriginalItems.size(); i < size; i++) {
                  Item item = mOriginalItems.get(i);
                  if (item.isSelected()) {
                      selections.add(item);
                  }
              }
              return selections;
          } else {
              return mItemAdapter.getFastAdapter().getSelectedItems();
          }
      }
docs: helper method to get all selections from the ItemAdapter's original item list
  
  @return a Set with the selected items out of all items in this itemAdapter (not the listed ones)