code: def test_from_empty_polygons(self):
      masks = BitMasks.from_polygon_masks([], 100, 100)
      self.assertEqual(masks.tensor.shape, (0, 100, 100))
  
file_path: detectron2/tests/structures/test_masks.py
imports: import unittest
  import torch
  from detectron2.structures.masks import BitMasks, PolygonMasks, polygons_to_bitmask
label_desc: Use image node_id 2 for calling the TestBitMask obj's underlying member method code with example usage: obj.test_from_empty_polygons() without return types