Returns the value of the first element with the given route. 
      Syntax
         
         public abstract String getValue (String... route) throws IllegalArgumentException
       
      Parameters
         
         
            - 
               route – 
               The route to the element
            
 
         
       
      Returns
         The value of the first element or null if there is no such element
      Exceptions
         
         
            - 
               IllegalArgumentException – 
               if the argument is null.