code: def continuous_eval(self):
      
      for ckpt_path in next_checkpoint(self._hparams.model_dir,
                                       self._hparams.eval_timeout_mins):
        # Skip zero'th step.
        train_step = decoding.get_step_from_ckpt_path(ckpt_path)
        if train_step == 0:
          tf.logging.info("Skipping evaluation at step 0")
          continue
        self.evaluate()
docs: Evaluate until checkpoints stop being produced.