docs: def resend_unprocessed(self):
          """ Resend all unprocessed items """
          LOG.info("Re-sending %d unprocessed items.", len(self._unprocessed))
  
          while self._unprocessed:
              to_resend = self._unprocessed[:MAX_WRITE_BATCH]
              self._unprocessed = self._unprocessed[MAX_WRITE_BATCH:]
              LOG.info("Sending %d items", len(to_resend))
              self._write(to_resend)
              LOG.info("%d unprocessed items left", len(self._unprocessed))