code: def test_mask(self):
      test_field = CnTextField(sents[0])
      self.assertEqual(
          [
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
              0,
          ],
          test_field.mask,
      )
  
imports: import unittest
  from textflint.input.component.field.cn_text_field import *
label_desc: Use image node_id 4 for calling the TestCnTextField obj's underlying member method code with example usage: obj.test_mask() without return types