code: def test_empty_cat(self):
      x = RotatedBoxes.cat([])
      self.assertTrue(x.tensor.shape, (0, 5))
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import logging
  import math
  import random
  import unittest
  import torch
  from fvcore.common.benchmark import benchmark
  from detectron2.layers.rotated_boxes import pairwise_iou_rotated
  from detectron2.structures.boxes import Boxes
  from detectron2.structures.rotated_boxes import RotatedBoxes, pairwise_iou
  from detectron2.utils.testing import reload_script_model
label_desc: Use image node_id 11 for calling the TestRotatedBoxesStructure obj's underlying member method code with example usage: obj.test_empty_cat() without return types