import tensorflow as tf

          # https://en.wikipedia.org/wiki/Matthews_correlation_coefficient
          tp, tp_op = tf.metrics.true_positives(
              predictions, label_ids, weights=is_real_example)
          tn, tn_op = tf.metrics.true_negatives(
              predictions, label_ids, weights=is_real_example)
          fp, fp_op = tf.metrics.false_positives(
              predictions, label_ids, weights=is_real_example)
          fn, fn_op = tf.metrics.false_negatives(
              predictions, label_ids, weights=is_real_example)

