code: def _on_io_events(self, fd=None, _events=None):
          
          if fd not in self._connections:
              LOGGER.warning('Received IO event for non-existing connection')
              return
          self._poll_connection(fd)
docs: Invoked by Tornado's IOLoop when there are events for the fd
  
          :param int fd: The file descriptor for the event
          :param int _events: The events raised