subtitle method
Implementation
subtitle(IRef contact) {
final lines = <String?>[];
// final operationInfo = this.operationInfoOrDefault;
lines.addAll(taskDescription.toStringList());
lines.add(setup?.asFact()?.subtitle(contact));
String subtitle = "";
subtitle += isCompleted ? "Completed: " : "Due: ";
subtitle += formattedDueLabel;
lines.add(subtitle);
return lines.where((str) => str.isNotNullOrBlank).join("\n");
}