toString method
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() {
  List<String> validOptionNames = [];
  RouteMapObjectDisplayFlag.values.forEach((element) {
    if (this.contains(element)) {
      validOptionNames.add(element.name);
    }
  });
  return "${this.runtimeType}: ${validOptionNames.join(', ')}";
}