code: def test_transform(self):
      trans_data = swap_ins.transform(data_sample)
      self.assertTrue(len(trans_data) == 1)
      self.assertEqual("小明喜欢看电影。", trans_data[0].get_value("x"))
      self.assertEqual(
          ["B", "E", "B", "E", "S", "B", "E", "S"],
          trans_data[0].get_value("y"),
      )
      self.assertTrue([0, 0, 0, 0, 0, 2, 2, 0] == trans_data[0].mask)
      trans_data = swap_ins.transform(
          CWSSample({"x": "玩具厂 大量 生产 玩具 。", "y": []})
      )
      self.assertEqual(1, len(trans_data))
  
file_path: textflint/test/generation/transformation/CWS/test_cn_mlm.py
imports: import unittest
  from textflint.generation.transformation.CWS.cn_mlm import CnMLM
  from textflint.input.component.sample.cws_sample import CWSSample
label_desc: Use image node_id 4 for calling the TestCnMLM obj's underlying member method code with example usage: obj.test_transform() without return types