/// <summary>
 /// Visits all the children of the specified element
 /// </summary>
 /// <param name="element">the element of which to visit their children</param>
 protected virtual void VisitChildren(SvgElement element)
 {
     if (element == null)
     {
         return;
     }
     foreach (var child in element.GetChildren())
     {
         Visit(child);
     }
 }