code: def decoded_output_boxes(self):
          
          anchors = tf.tile(tf.expand_dims(self.proposals.boxes, 1),
                            [1, cfg.DATA.NUM_CLASS, 1])   # N x #class x 4
          decoded_boxes = decode_bbox_target(
              self.box_logits / self.bbox_regression_weights,
              anchors
          )
          return decoded_boxes
docs: Returns: N x #class x 4