docs: def readline(self):
          """
          Waits for a line from the Herald client
          """
          content = {"session_id": self._session}
          prompt_msg = self._herald.send(
              self._peer, beans.Message(MSG_CLIENT_PROMPT, content))
          if prompt_msg.subject == MSG_SERVER_CLOSE:
              # Client closed its shell
              raise EOFError
  
          return prompt_msg.content