protocol CustomPlaygroundQuickLookable A type that explicitly supplies its own PlaygroundQuickLook. Instances of any type can be PlaygroundQuickLook(reflect:)'ed upon, but if you are not satisfied with the PlaygroundQuickLook supplied for your type by default, you can make it conform to CustomPlaygroundQuickLookable and return a custom PlaygroundQuickLook. Import import Swift Instance Methods func customPlaygroundQuickLook() Required Returns the PlaygroundQuickLook for self. Note: If Self has value semantics, the PlaygroundQuickLook should be unaffected by subsequent mutations of self. Declaration func customPlaygroundQuickLook() -> PlaygroundQuickLook