Set a variable from a Data group

You probably have figured it out by now but just in case, here's an example.

Data group list:

ltm data-group internal /Common/select_server {
    records {
	server {
            data a
        }
    }
    type string
}

And the rule: 

when HTTP_REQUEST {

  # Below is the droid... I mean line you're looking for
  set selected_server [class lookup "server" select_server]
  HTTP::respond 200 content $selected_server

}

 Good luck!

Kind regards,
Patrik