title: swift ios Set transition style and orientation programmatically of PageViewController
body: <p>I have View Controller and its super class is UIPageViewController
  I want to its transition style and orientation.</p>
  
  <pre><code>var navigationOrientation: UIPageViewControllerNavigationOrientation { 
  get }
  var transitionStyle: UIPageViewControllerTransitionStyle { get }
  </code></pre>
  
  <p>The value of this property is set when the page view controller is initialized, and cannot be changed.
   where exactly page is initialized in view controller and how to set these properties.</p>