docs: def getCallBack(self, ps, post, action):
          '''post -- POST HTTP value
             action -- SOAP Action value
          '''
          node = self.getNode(post)
          if node is None:
              raise NoSuchFunction
          if node.authorize(None, post, action):
              return node.getOperation(ps, action)
          else:
              raise NotAuthorized, "Authorization failed for method %s" % action