 
      - Returns: `self` to allow for additional method chaining.
      */
-    public final func set(delay: Foundation.TimeInterval) -> Tween {
+    @discardableResult public final func set(delay: Foundation.TimeInterval) -> Tween {
         self.delay = delay
         return self
     }


     - Returns: `self` to allow for additional method chaining.
     */
    public final func set(callback: @escaping Callback, for stateChange: TweenStateChange) -> Tween {
        self.callback(set: stateChange, value: callback)
        return self
    }


 ```
 let tween = self.tween(property: .x(50.0), duration: 1.0)
    .set(ease: Ease.backOut)
    .set(delay: 0.5)
    .set(callback: { ... }, for: TweenStateChange.complete)
 ```
