question: @ Nullable public static String openDialog ( Module module , String title , boolean includeAll , @ Nullable Condition < PsiClass > filter , @ NotNull String ... classes ) { final Project project = module . getProject ( ) ; final DumbService dumbService = DumbService . getInstance ( project ) ; if ( dumbService . isDumb ( ) ) { dumbService . showDumbModeNotification ( String . format ( "%1$s are not available while indices are updating." , title ) ) ; return null ; } final ChooseClassDialog dialog = new ChooseClassDialog ( module , title , includeAll , filter , classes ) ; return dialog . showAndGet ( ) ? dialog . getClassName ( ) : null ; }
target:  Open a dialog if indices are available, otherwise show an error message.