title: cannot convert value of type [anyhashable: any] to [string: any]
body: <pre><code> let darkGray = UIColor.darkGray
      let lightGray = UIColor.lightGray
      let white = UIColor.white
      // Navigation bar background.
      UINavigationBar.appearance().barTintColor = darkGray
      UINavigationBar.appearance().tintColor = lightGray
      // Color of typed text in the search bar.
      let searchBarTextAttributes: [AnyHashable: Any] = [NSForegroundColorAttributeName: lightGray, NSFontAttributeName: UIFont.systemFont(ofSize: CGFloat(UIFont.systemFontSize))]
      UITextField.appearance(whenContainedInInstancesOf: [UISearchBar.self]).defaultTextAttributes = searchBarTextAttributes as! [String : Any]
      // Color of the placeholder text in the search bar prior to text entry.
      let placeholderAttributes: [AnyHashable: Any] = [NSForegroundColorAttributeName: white, NSFontAttributeName: UIFont.systemFont(ofSize: CGFloat(UIFont.systemFontSize))]
      // Color of the default search text.
      // NOTE: In a production scenario, "Search" would be a localized string.
      let attributedPlaceholder = NSAttributedString( string: "Search", attributes: placeholderAttributes)
      UITextField.appearance(whenContainedInInstancesOf: [UISearchBar.self]).attributedPlaceholder = attributedPlaceholder
  </code></pre>
  
  <p>In the let attributedPlaceholder I'm coming up with an error, wondering if someone could shed some light on this for me?</p>