init()
func contains(Self) -> Bool
func formIntersection(Self)
func formSymmetricDifference(Self)
func formUnion(Self)
func insert(Self.Element) -> (inserted: Bool, memberAfterInsert: Self.Element)
func intersection(Self) -> Self
func remove(Self.Element) -> Self.Element?
func symmetricDifference(Self) -> Self
func union(Self) -> Self
func update(with: Self.Element) -> Self.Element?