An SKNode can have userData to store arbitrary data.

I set the property "isEvil" on two SKNodes. Then I want to check if both nodes are evil. 

```
var hero = SKNode()
hero.userData = ["isEvil": false]

var enemy = SKNode()
enemy.userData = ["isEvil": true]

if hero.userData!["isEvil"] == enemy.userData!["isEvil"] {
  println("the here and the enemy are equally evil!")
}

```

The `if` line gives an error: `Type 'AnyObject?' does not conform to protocol '_RawOptionSetType'`.

**How am I supposed to compare these values?** 

According to [docs](https://developer.apple.com/library/ios/documentation/SpriteKit/Reference/SKNode_Ref/index.html#//apple_ref/occ/instp/SKNode/userData), SKNode.userData is `NSMutableDictionary?`. Since it is optional, I am sure to unwrap the values using `!`.