code: def decoded_output_boxes_class_agnostic(self):
          
          assert self._bbox_class_agnostic
          box_logits = tf.reshape(self.box_logits, [-1, 4])
          decoded = decode_bbox_target(
              box_logits / self.bbox_regression_weights,
              self.proposals.boxes
          )
          return decoded
docs: Returns: Nx4