text: import numpy as np
  import tensorflow as tf
  from utils import box_utils
  
  class SSDTargetTransform:
      def __init__(self, center_form_priors, center_variance, size_variance, iou_threshold):
          self.center_form_priors = center_form_priors
          self.corner_form_priors = box_utils.center_form_to_corner_form(center_form_priors)
          self.center_variance = center_variance
          self.size_variance = size_variance
          self.iou_threshold = iou_threshold
  
      def __call__(self, gt_boxes, gt_labels):
          if type(gt_boxes) is np.ndarray:
              gt_boxes = tf.convert_to_tensor(gt_boxes) 
          if type(gt_labels) is np.ndarray:
              gt_labels = tf.convert_to_tensor(gt_labels)
          boxes, labels = box_utils.assign_priors(gt_boxes, gt_labels,
                                                  self.corner_form_priors, self.iou_threshold)
          boxes = box_utils.corner_form_to_center_form(boxes)
          locations = box_utils.convert_boxes_to_locations(boxes, self.center_form_priors, self.center_variance, self.size_variance)
          return locations, labels