This being made, building the framework for a macOS target, as described on the file's initial comments, makes us able to run the Playground without any issues.
Xcode Version 9.0 (9A235)
While the use of TimeInterval is understandable from the perspective
of maintaining parity with the Objective-C function PMKAfter, it's not
quite as strongly typed as DispatchTimeInterval. Also, what's really
going on is a dispatch after a deadline and so support for both seconds
and DispatchTimeInterval seem warranted.
