/// <summary>
 /// Add the specified hierarchy element.
 /// </summary>
 /// <param name="element">The hierarchy element to add.</param>
 private void AddHierarchyElement(DocumentRange element)
 {
     if (_lastHierarchyElement == null)
     {
         _page.AddContent(element);
     }
     else
     {
         _lastHierarchyElement.AddElement(element);
     }
     _lastHierarchyElement = element;
 }