Search for a sets elements in Swift

Forums:

let chars: Set<Character> = ["A""B""C""D"]
let containA = chars.contains("A")
//containA is true

let containE = chars.contains("E");
//containE is False

let chars2: Set<Character> = ["A""B"]
let containAll = chars.isSupersetOf(chars2)
//containAll is true