setThemeMode method
Implementation
void setThemeMode(ThemeMode? value, [bool notify = true]) {
// No work if null value passed.
if (value == null) return;
// Do not perform any work if new and old value are identical.
if (value == _themeMode) return;
// Otherwise, assign new value to private property.
_themeMode = value;
// Inform all listeners a change has occurred, if notify flag is true.
if (notify) notifyListeners();
// Persist the change to whatever storage is used with the ThemeService.
unawaited(_themeService.save(Store.keyThemeMode, value));
}