public void find_node()
 {
     graph.FindNode(FakeKeys.Key10).Key.ShouldBe(FakeKeys.Key10);
     graph.FindNode(FakeKeys.Key8).Key.ShouldBe(FakeKeys.Key8);
     graph.FindNode(FakeKeys.Key4).Key.ShouldBe(FakeKeys.Key4);
 }