AD Plugin - Find Groups of an User

Hello,

I am still trying to get more informations of an user from AD. I tryed the following code with an AD_User as Input:

var test = User.memberOf;

System.log(test);

But the result is:

[2014-03-10 21:04:53.854] [I] undefined

The server.log says the following:

[DynamicWrapper] Property named 'memberOf' not found on object : AD_User

But I know that this property exists in AD_User.Can someone please help me out?

Thanks in advance.

Chris