code: def set_combine_stderr(self, combine):
          
          data = bytes()
          self.lock.acquire()
          try:
              old = self.combine_stderr
              self.combine_stderr = combine
              if combine and not old:
                  # copy old stderr buffer into primary buffer
                  data = self.in_stderr_buffer.empty()
          finally:
              self.lock.release()
          if len(data) > 0:
              self._feed(data)
          return old
docs: Set whether stderr should be combined into stdout on this channel.
          The default is ``False``, but in some cases it may be convenient to
          have both streams combined.
  
          If this is ``False``, and `exec_command` is called (or ``invoke_shell``
          with no pty), output to stderr will not show up through the `recv`
          and `recv_ready` calls.  You will have to use `recv_stderr` and
          `recv_stderr_ready` to get stderr output.
  
          If this is ``True``, data will never show up via `recv_stderr` or
          `recv_stderr_ready`.
  
          :param bool combine:
              ``True`` if stderr output should be combined into stdout on this
              channel.
          :return: the previous setting (a `bool`).
  
          .. versionadded:: 1.1