Add a sub :class:`RpcHandler` with prefix ``prefix``.

        :keyword prefix: a string defining the prefix of the subhandler
        :keyword handler: the sub-handler.

def putSubHandler(self, prefix, handler):
        '''Add a sub :class:`RpcHandler` with prefix ``prefix``.

        :keyword prefix: a string defining the prefix of the subhandler
        :keyword handler: the sub-handler.
        '''
        self.subHandlers[prefix] = handler
        handler._parent = self
        return self