import tensorflow as tf

        matched_gt_boxes)
    matched_gt_classes = tf.where(
        background_indicator,
        tf.zeros_like(matched_gt_classes),
        matched_gt_classes)
    matched_gt_indices = tf.where(
        background_indicator,
        -tf.ones_like(matched_gt_indices),
        matched_gt_indices)

    return (matched_gt_boxes, matched_gt_classes, matched_gt_indices,
            positive_matches, negative_matches, ignored_matches)

  def get_config(self):
