code: public Object resetHardState(FacesContext context)
      {
          if (_transientState != null)
          {
              _transientState.clear();
          }
          if (_deltas != null && !_deltas.isEmpty() && isInitialStateMarked())
          {
              clearFullStateMap(context);
          }
          return saveState(context);
      }
docs: Try to reset the state and then check if the reset was succesful or not,
  calling saveState().