title: XCUIElement - Obtain Image value
body: <p>I have an variable that's of type <code>.Image</code> and class <code>XCUIElement</code>. Something like this: </p>
  
  <p><code>var image = app.descendantsMatchingType(.Image).elementAtIndex(0)</code></p>
  
  <p>Is there a way I can extract the actual image so I can compare it to another image? </p>
  
  <p>I've tried caling the <code>value</code> method, but it returns a string. Casting it to a <code>UIImage</code> always fails. </p>