ServiceObject.IsValid() method

[Robert Olson]

this is in place. We also have .Implements(method), which returns 1 if that 
object is valid and implements that method. From the test program:

def try_url(url):

     print "test ", url

     h = Client.Handle(url)

     ret = h.IsValid()
     print "IsValid %s returns '%s'" % (url, ret)

     ret = h.Implements("method")
     print "Implements 'method' returns %s" % (ret)

     ret = h.Implements("methodX")
     print "Implements 'methodX' returns %s" % (ret)