/// <summary>
 /// Converts a navigable to an XElement if it can be read as an element.
 /// </summary>
 /// <param name="navigable"></param>
 /// <returns></returns>
 public static Opt <XElement> ToXElementOpt(this IXPathNavigable navigable)
 {
     return(navigable.ToXNode().ToXElementOpt());
 }