toString method Null safety
override
    A string representation of this object.
Some classes have a default textual representation,
often paired with a static parse function (like int.parse).
These classes will provide the textual representation as
their string representation.
Other classes have no meaningful textual representation
that a program will care about.
Such classes will typically override toString to provide
useful information when inspecting the object,
mainly for debugging or logging.
Implementation
@override
String toString() {
  final List<String> features = <String>[];
  if (accessibleNavigation) {
    features.add('accessibleNavigation');
  }
  if (invertColors) {
    features.add('invertColors');
  }
  if (disableAnimations) {
    features.add('disableAnimations');
  }
  if (boldText) {
    features.add('boldText');
  }
  if (reduceMotion) {
    features.add('reduceMotion');
  }
  if (highContrast) {
    features.add('highContrast');
  }
  if (onOffSwitchLabels) {
    features.add('onOffSwitchLabels');
  }
  return 'AccessibilityFeatures$features';
}