docs: def function(self, func_name):
          """
          Returns the Function instance associated with the given func_name, or raises a
          RpcException if no function matches.
          """
          if self.functions.has_key(func_name):
              return self.functions[func_name]
          else:
              raise RpcException(ERR_METHOD_NOT_FOUND, 
                                 "%s: Unknown function: '%s'", self.name, func_name)