code: def validation_metrics(self):
          
  
          if (self._validation_iterator is None) or (self._validation_metrics is None):
              raise AttributeError('Validation is not setup.')
  
          n = 0.0
          metric_sums = [0.0] * len(self._validation_metrics)
          self._sess.run(self._validation_iterator.initializer)
          while True:
              try:
                  metrics = self._sess.run(self._validation_metrics)
                  for i, m in enumerate(metrics):
                      metric_sums[i] += m
                  n += 1.0
              except tf.errors.OutOfRangeError:
                  break
          for i, m in enumerate(metric_sums):
              metric_sums[i] = metric_sums[i] / n
          return zip(self._validation_metrics, metric_sums)
docs: A helper function to compute validation related metrics