Process a string in batch mode.

        Arguments:
            content: A unicode string representing the content to be processed.

def batch_string(self, content):
        """Process a string in batch mode.

        Arguments:
            content: A unicode string representing the content to be processed.
        """
        pipe_send, pipe_recv = multiprocessing.Pipe()
        self._pipe_end = pipe_recv
        proc = multiprocessing.Process(target = self.cmdloop)
        for line in content.split('\n'):
            pipe_send.send(line)
        pipe_send.close()
        proc.start()
        proc.join()