code: private void initializeOverrideBackButton(final SharedPreferences sharedPreferences) {
          String key = getString(R.string.override_navigation_icon_preference_key);
          boolean defaultValue = Boolean.valueOf(
                  getString(R.string.override_navigation_icon_preference_default_value));
          boolean overrideNavigationIcon = sharedPreferences.getBoolean(key, defaultValue);
          overrideNavigationIcon(overrideNavigationIcon);
      }
docs: Initializes, whether the action bar's back button should be overridden, or not.
  
  @param sharedPreferences
  The shared preferences, which should be used, as an instance of the type {@link
  SharedPreferences}