undo method
Implementation
void undo({bool deleteOnly = false, bool silent = false}) {
if ( !deleteOnly )
// Remove this command and all previous commands from the stack
stack?.removeUpToAndIncluding(this);
// remove from parent
if ( parent != null) {
parent!.children.remove(this);
if (parent!.children.isEmpty)
parent!.undo(silent: silent, deleteOnly: deleteOnly);
}
}