title: swift 4.0: Overriding 'prepare' must be as available as declaration it overrides
body: <p>I was trying to integrate Apple's ARKit example app into my app. As ARKit is only an additional feature, so I need to support lower versions of iOS. I added @available(iOS 11.0, *) tag to all the ARKit example app classes...It almost works except this 1 error: "Overriding 'prepare' must be as available as declaration it overrides". Any idea how can I resolve this issue ?</p>
  
  <p><a href="https://i.stack.imgur.com/zfuTL.png" rel="noreferrer">Xcode error image</a></p>