code: function pushDocument(doc) {
      if (!(doc instanceof Document)) {
          console.warn('Cannot navigate to the document.', doc);
          return;
      }
      navigationDocument.pushDocument(doc);
  }
docs: Pushes a given document to the navigation stack after applying all the default page level handlers.
  
  @private
  
  @param  {Document} doc       The document to push to the navigation stack