code: def send_stderr(self, s):
          
  
          m = Message()
          m.add_byte(cMSG_CHANNEL_EXTENDED_DATA)
          m.add_int(self.remote_chanid)
          m.add_int(1)
          return self._send(s, m)
docs: Send data to the channel on the "stderr" stream.  This is normally
          only used by servers to send output from shell commands -- clients
          won't use this.  Returns the number of bytes sent, or 0 if the channel
          stream is closed.  Applications are responsible for checking that all
          data has been sent: if only some of the data was transmitted, the
          application needs to attempt delivery of the remaining data.
  
          :param str s: data to send.
          :return: number of bytes actually sent, as an `int`.
  
          :raises socket.timeout:
              if no data could be sent before the timeout set by `settimeout`.
  
          .. versionadded:: 1.1