import tensorflow as tf

        boxes (num_priors, 4): real values for priors.
        labels (num_priors): labels for priors.
    """
    # size: num_priors x num_targets
    ious = iou_of(tf.expand_dims(gt_boxes, axis=0), tf.expand_dims(corner_form_priors, axis=1))

    # size: num_priors
    best_target_per_prior = tf.math.reduce_max(ious, axis=1)
