How to use Expression to Mask Path vertices

Hi guys,

In Expression Language Reference(https://helpx.adobe.com/after-effects/using/expression-language-reference.html), I find an method called "points()";

and there is an example like:

• Example 2

The example reads the coordinates of the first vertex of Mask 1 on Dark Gray Solid 1 and converts them to composition coordinates. Apply this to a 2D point control of an effect, such as Write-on or CC Particle Systems II, to make the effect trace or track the first point of an animated mask. Duplicate the effect and change the path points index value ([0]) to trace or track the other points of the mask.

myLayer = thisComp.layer(2);
myLayer.toComp(myLayer.mask("Mask 1").maskPath.points()[0]);

emm...

but when I try this, I get en error message saied:

points() method is undefined.....

So I confused about points() method,