code: def proposal_metrics(iou):
      
      # find best roi for each gt, for summary only
      best_iou = tf.reduce_max(iou, axis=0)
      mean_best_iou = tf.reduce_mean(best_iou, name='best_iou_per_gt')
      summaries = [mean_best_iou]
      with tf.device('/cpu:0'):
          for th in [0.3, 0.5]:
              recall = tf.truediv(
                  tf.count_nonzero(best_iou >= th),
                  tf.size(best_iou, out_type=tf.int64),
                  name='recall_iou{}'.format(th))
              summaries.append(recall)
      add_moving_summary(*summaries)
docs: Add summaries for RPN proposals.
  
      Args:
          iou: nxm, #proposal x #gt