code: @Override
      public void notifyChanged(IChemObjectChangeEvent evt) {
          if (getNotification() && getListenerCount() > 0) {
              List<IChemObjectListener> listeners = lazyChemObjectListeners();
              for (Object listener : listeners) {
                  ((IChemObjectListener) listener).stateChanged(evt);
              }
          }
      }
docs: This should be triggered by an method that changes the content of an object
  to that the registered listeners can react to it. This is a version of
  notifyChanged() which allows to propagate a change event while preserving
  the original origin.
  
  @param  evt  A ChemObjectChangeEvent pointing to the source of where
  the change happend