Returns: N x #class x 4

def decoded_output_boxes(self):
        """ Returns: N x #class x 4 """
        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