question: private void ensureParentsVisible ( ) { Set < Object > parentNodes = new HashSet < Object > ( ) ; for ( Object node : visibleNodes ) { Object parentNode = parentProvider . getParent ( node ) ; while ( parentNode != null ) { parentNodes . add ( parentNode ) ; parentNode = parentProvider . getParent ( parentNode ) ; } } visibleNodes . addAll ( parentNodes ) ; }
target:  Sets all parents of the visible nodes visible.