is there anyway to test my extension methods in the playground

Question

I was trying out the sample from the apple developer blog, but i notice that the playground does not seem to see the extension. Is this possible yet?

func valuesForKeys2(keys: [Key]) -> [Value?] {
    //this iterates throw each key and executes a function
    //on the class for each value
    return keys.map { self[$0]}
}