code: def detach(self) -> iostream.IOStream:
          
          self._finished = True
          # TODO: add detach to HTTPConnection?
          return self.request.connection.detach()
docs: Take control of the underlying stream.
  
          Returns the underlying `.IOStream` object and stops all
          further HTTP processing. Intended for implementing protocols
          like websockets that tunnel over an HTTP handshake.
  
          This method is only supported when HTTP/1.1 is used.
  
          .. versionadded:: 5.1