Returns the Function instance associated with the given func_name, or raises a
        RpcException if no function matches.

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)