code: def test_words_length(self):
      test_field = CnTextField("小明去上海")
      self.assertRaises(ValueError, CnTextField, {})
      self.assertEqual(3, test_field.words_length)
  
      test_field = CnTextField(sents[0])
      self.assertEqual(17, test_field.words_length)
  
      test_field = CnTextField("")
      self.assertEqual(0, test_field.words_length)
  
imports: import unittest
  from textflint.input.component.field.cn_text_field import *
label_desc: Use image node_id 2 for calling the TestCnTextField obj's underlying member method code with example usage: obj.test_words_length() without return types