code: void onButtonFired(final ActionEvent event) {
  
          final Optional<Button> b = getTarget(event, Button.class);
  
          final Optional<UniqueKey<? extends Model>> data = getUserData(b, StackWaves.PAGE_MODEL_KEY);
  
          if (data.isPresent()) {
              model().sendWave(StackWaves.SHOW_PAGE_MODEL,
                               WBuilder.waveData(StackWaves.PAGE_MODEL_KEY, data.get()),
                               WBuilder.waveData(StackWaves.STACK_NAME, "DemoStack"));
  
          }
      }
docs: When a button is fired display the related ModuleModel.
  
  @param event the action event