What is GetBoundaryPolygon (in DetectedPlane class)

I have been working on a project in ARCore and I am trying to limit the size of plane that is detected. The documentation says that the function GetBoundaryPolygon takes a list of Vector3 and uses it to make a boundary polygon. However, I tried using it but no success.

I made a list of Vector3:

Code (CSharp):

1. List<Vector3> boundary = new List<Vector3>();
2.  
3. boundary.Add (new Vector3(0, 0 ,0 ));
4.         boundary.Add (new Vector3 (0, 0, 1));
5.         boundary.Add (new Vector3 (1, 0, 1));
6.         boundary.Add (new Vector3(1, 0, -1));

And then I passed it in my "Update Method" like this:

Code (CSharp):

1.  
2. //We have touched the screen. We do a raycast to see that the touch hits a plane
3.             TrackableHit hit;
4.             var rayCastFilter = TrackableHitFlags.PlaneWithinBounds | TrackableHitFlags.PlaneWithinPolygon;
5.  
6.             if (Frame.Raycast (touch.position.x, touch.position.y, rayCastFilter, out hit) && gameObject != null) {
7.                 //Create anchor to track the hitpoint (Session Class Used)
8.                 var anchor = Session.CreateAnchor (hit.Pose, hit.Trackable);
9.                 //Place the environment at the anchor and make it as anchor's child
10.  
11.                 environment.transform.position = anchor.transform.position;
12.                 //environment.transform.rotation = Quaternion.identity;
13.                 //environment.transform.Rotate(0, 90, 0, Space.Self);
14.                 environment.transform.parent = anchor.transform;
15.                 environment.SetActive (true);
16.  
17.  
18.                 //Instantiate an object as a child of the anchor
19.                 //var placedObject = Instantiate (environment, hit.Pose.position, Quaternion.identity, anchor.transform);
20.  
21.                 //Turn on the Score Canvas
22.                 canvas_score.gameObject.SetActive(true);
23.  
24.                 //Turn on the joystick canvas
25.                 canvas_joystick.gameObject.SetActive(true);
26.  
27.                 //Using Trackable as detectedPlane
28.                 DetectedPlane dp = hit.Trackable as DetectedPlane;
29.                 dp.GetBoundaryPolygon (boundary);
30.                 //Vector3 test_pos = new Vector3(hit.Pose.position.x, hit.Pose.position.y, dp.ExtentZ);