code: def test_flip_polygons(self):
      t = RandomFlip(prob=1.0, direction="horizontal")
      results = t.flip_polygons(
          self.data_info["gt_polygons"], (30, 40), "horizontal"
      )
      self.assertIsInstance(results, list)
      self.assertIsInstance(results[0], np.ndarray)
      self.assertTrue(
          (
              results[0]
              == np.array(
                  [30.0, 5.0, 20.0, 5.0, 20.0, 10.0, 30.0, 10.0]
              )
          ).all()
      )
  
      results = t.flip_polygons(
          self.data_info["gt_polygons"], (30, 40), "vertical"
      )
      self.assertIsInstance(results, list)
      self.assertIsInstance(results[0], np.ndarray)
      self.assertTrue(
          (
              results[0]
              == np.array(
                  [10.0, 25.0, 20.0, 25.0, 20.0, 20.0, 10.0, 20.0]
              )
          ).all()
      )
      results = t.flip_polygons(
          self.data_info["gt_polygons"], (30, 40), "diagonal"
      )
      self.assertIsInstance(results, list)
      self.assertIsInstance(results[0], np.ndarray)
      self.assertTrue(
          (
              results[0]
              == np.array(
                  [30.0, 25.0, 20.0, 25.0, 20.0, 20.0, 30.0, 20.0]
              )
          ).all()
      )
      with self.assertRaises(ValueError):
          t.flip_polygons(
              self.data_info["gt_polygons"], (30, 40), "mmocr"
          )
  
imports: import copy
  import unittest
  import unittest.mock
  import numpy
  from mmcv.transforms import Pad, RandomResize
  from mmocr.datasets.transforms import BoundedScaleAspectJitter, RandomCrop, RandomFlip, Resize, ShortScaleAspectJitter, SourceImagePad, TextDetRandomCrop, TextDetRandomCropFlip
  from mmocr.utils import bbox2poly, poly2shapely
label_desc: Use image node_id 2 for calling the TestRandomFlip obj's underlying member method code with example usage: obj.test_flip_polygons() without return types