code: public void showView(Modality modality) {
          if (! isPrimaryStageView && (stage == null || currentStageModality != modality)) {
              stage = createStage(modality);
          }
          stage.show();
      }
docs: Shows the FxmlView instance on a top level {@link Window}
  
  @param modality
  See {@code javafx.stage.Modality}.