Tuple <ChangedAncestorInfo <TNode>, IEnumerable <TNode> > ancChangedRange()
{
bool rootChanged = !object.Equals(PreOldRoot, _self.Upstream().Last());
var arg = new ChangedAncestorInfo <TNode>(_self, OldParent, oldIndex, rootChanged);
return(Tuple.Create(arg, _self.Levelorder()));
}
