code: private boolean isTitleAlreadyUsed(@NonNull final CharSequence title) {
          for (NavigationPreference navigationPreference : getAllNavigationPreferences()) {
              if (title.equals(navigationPreference.getTitle())) {
                  return true;
              }
          }
  
          return false;
      }
docs: Returns, whether a preference header, which has a specific title, has already been added to
  the activity, or not.
  
  @param title
  The title, whose presence should be checked, as an instance of the class {@link
  CharSequence}. The tile may not be null
  @return True, if a preference header, which has the given title, has already been added to
  the activity, false otherwise