init<S>(S)
init(arrayLiteral: Self.Element...)
var isEmpty: Bool
func isDisjoint(with: Self) -> Bool
func isStrictSubset(of: Self) -> Bool
func isStrictSuperset(of: Self) -> Bool
func isSubset(of: Self) -> Bool
func isSuperset(of: Self) -> Bool
func subtract(Self)
func subtracting(Self) -> Self