code: def finish_raw(self, body: bytes, status: int = 200, content_type: Optional[str] = None):
          
          self.ret_val = body
          self.response = web.Response(body=body, status=status, content_type=content_type)
          logger.debug('finish: raw body(%d bytes)' % len(body))
          self._finish_end()
docs: Set raw response
          :param body:
          :param status:
          :param content_type:
          :return: