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Error when unity camera access is applied to vuforia 2.8

I am trying to implement the unity camera access by following the link below.

https://developer.vuforia.com/resources/dev-guide/unity-camera-image-access

However a error is encontered and i am using the laster version of vuforia (2.8)

Assets\NewBehaviourScript.cs(4,4): Error CS1501: No overload for method 'RegisterTrackerEventHandler' takes '1' arguments (CS1501) (Assembly-CSharp)

 

How can i solve it? 

thanks