code: private Bundle notifyOnPreviousStep() {
          Bundle result = null;
          NavigationPreference selectedNavigationPreference =
                  navigationFragment.getSelectedNavigationPreference();
  
          if (selectedNavigationPreference != null && preferenceFragment != null) {
              for (WizardListener listener : wizardListeners) {
                  Bundle bundle =
                          listener.onPreviousStep(selectedNavigationPreference, preferenceFragment,
                                  selectedPreferenceFragmentArguments);
  
                  if (bundle != null) {
                      if (result == null) {
                          result = new Bundle();
                      }
  
                      result.putAll(bundle);
                  }
              }
          }
  
          return result;
      }
docs: Notifies all registered listeners that the user wants to navigate to the previous step of the
  wizard.
  
  @return A bundle, which may contain key-value pairs, which have been acquired in the wizard,
  if navigating to the previous step of the wizard should be allowed, as an instance of the
  class {@link Bundle}, null otherwise