     }
     self.navigationController?.pushViewController(vc, animated: true)
   }
-  
+
 }
 
 // UIScrollViewDelegate
 extension MDCDragonsController {
-  
+
   func scrollViewDidScroll(_ scrollView: UIScrollView) {
     if scrollView == headerViewController.headerView.trackingScrollView {
       self.headerViewController.headerView.trackingScrollDidScroll()
       self.adjustLogoForScrollView(scrollView)
     }
   }
-  
+
   func scrollViewDidEndDragging( _ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
     let headerView = headerViewController.headerView
     if scrollView == headerView.trackingScrollView {
       headerView.trackingScrollDidEndDraggingWillDecelerate(decelerate)
     }
   }
-  
+
   func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
     if scrollView == headerViewController.headerView.trackingScrollView {
       self.headerViewController.headerView.trackingScrollDidEndDecelerating()
     }
   }
-  
+
   func scrollViewWillEndDragging(_ scrollView: UIScrollView,
                                           withVelocity velocity: CGPoint,
                                           targetContentOffset: UnsafeMutablePointer<CGPoint>) {

          NSFontAttributeName: UIFont.systemFont(ofSize: 16) ]
      container.isTopLayoutGuideAdjustmentEnabled = true
      vc.title = nodeData.node.title
      
      let headerView = container.appBar.headerViewController.headerView
      if let collectionVC = vc as? UICollectionViewController {
        headerView.trackingScrollView = collectionVC.collectionView

      nodeData.expanded = !nodeData.expanded
    }
  }

  func setupTransition(nodeData: DragonCell) {
    var vc = nodeData.node.createExampleViewController()
    if !vc.responds(to: NSSelectorFromString("catalogShouldHideNavigation")) {
