code: def test_pos_tags(self):
      sent = "今天天气很好。"
      test_field = CnTextField(sent)
      self.assertEqual(
          [
              ["nt", 0, 1],
              ["n", 2, 3],
              ["d", 4, 4],
              ["a", 5, 5],
              ["wp", 6, 6],
          ],
          test_field.pos_tags(),
      )
      sent = ""
      test_field = CnTextField(sent)
      self.assertEqual([], test_field.pos_tags())
  
imports: import unittest
  from textflint.input.component.field.cn_text_field import *
label_desc: Use image node_id 7 for calling the TestCnTextField obj's underlying member method code with example usage: obj.test_pos_tags() without return types