       return source.isCancellationRequested
     }
   }
+
   internal init(state: State) {
     self.state = state
   }

*/
public let CancelledToken = CancellationTokenSource(cancelled: true).token

public enum State {
  case Cancelled
  case NotCancelled
  case Pending(CancellationTokenSource)

*/
public struct CancellationToken {

  private var state: State

  public var isCancellationRequested: Bool {
    switch state {
