   /// - returns: whether the cancellation was performed successfully.
 
   @discardableResult
-  public func cancel(_ reason: String = "") -> Bool
+  open func cancel(_ reason: String = "") -> Bool
   {
     return determine(Result.error(DeferredError.canceled(reason)))
   }

  ///
  /// - parameter task:  the closure to be enqueued

  public func notify(qos: DispatchQoS? = nil, task: @escaping (Result<Value>) -> Void)
  {
    var c = resultp.load(order: .acquire)
    if c == nil


  /// Change the state of this `TBD` from `.waiting` to `.executing`

  open override func beginExecution()
  {
    super.beginExecution()
  }
