final NamedObj container = (NamedObj) _getGraphModel().getRoot();
// Get the selection objects.
// NOTE: The order in the model must be respected.
HashSet namedObjSet = _getSelectionSet();
final List elements = container.sortContainedObjects(namedObjSet);
// Return if any is a derived object.
if (_checkForImplied(elements)) {
return;
}