code: @NonNull
      public final List<NavigationPreference> getAllNavigationPreferences() {
          return navigationFragment != null ? navigationFragment.getAllNavigationPreferences() :
                  Collections.<NavigationPreference>emptyList();
      }
docs: Returns a list, which contains all navigation preferences, which are contained by the
  activity.
  
  @return A list, which contains all navigation preferences, which are contained by the
  activity, as an instance of the type {@link List} or an empty collection, if no navigation
  preferences are contained by the activity