public static IEnumerable <LinkedListNode <T> > GetNextNodes <T>(this LinkedListNode <T> node) => node.AsEnumerable(n => n.Next).Skip(1);
public static IEnumerable <LinkedListNode <T> > GetPreviousNodes <T>(this LinkedListNode <T> node) => node.AsEnumerable(n => n.Previous).Skip(1);
public static int GetIndex <T>(this LinkedListNode <T> node) => node.AsEnumerable(n => n.Previous).Count() - 1;