code: def test_transformation(self):
      trans_sample = swap_ins.transform(data_sample)
      self.assertTrue(len(trans_sample) == 1)
      trans_sample = trans_sample[0]
      self.assertEqual(
          [0, 0, 2, 2, 2, 2, 2, 0, 0, 0], trans_sample.mask
      )
      self.assertEqual("来自中央电视台报道。", trans_sample.get_value("x"))
      self.assertEqual(
          ["B", "E", "B", "M", "M", "M", "E", "B", "E", "S"],
          trans_sample.get_value("y"),
      )
  
imports: import unittest
  from textflint.generation.transformation.CWS.swap_contraction import SwapContraction
  from textflint.input.component.sample.cws_sample import CWSSample
label_desc: Use image node_id 2 for calling the TestSwapContraction obj's underlying member method code with example usage: obj.test_transformation() without return types