title: Proper implementation of handleInputModeList in Custom Keyboard
body: <p>A new API has been added in iOS 10 to present the list of other keyboards the user can switch to - the same list that appears when users long press the globe on a system keyboard. The declaration of the function is as follows:<br>
  <code>func handleInputModeList(from view: UIView, with event: UIEvent)</code></p>
  
  <p>My question is, what's the proper way to generate a <code>UIEvent</code> to supply? I was planning to call this function using a <code>UILongPressGestureRecognizer</code> but this API doesn't reveal <code>UIEvent</code>s.</p>