/// <summary>
 /// This constructor defaults to UnchosenVertexNodeState.
 /// </summary>
 /// <param name="node"></param>
 protected internal VertexNodeStateContext(VertexNode node)
     : base(node, UnchosenVertexNodeState.Instance)
 {
 }
 protected internal VertexNodeStateContext(VertexNode node, VertexNodeState state)
     : base(node, state)
 {
 }