code: def test_empty_string(self):
      tagged_text = self.tagger.get_text_index_string("")
  
      self.assertEqual(tagged_text, "")
  
imports: from unittest import TestCase
  from chatterbot import languages
  from chatterbot import tagging
label_desc: Use image node_id 2 for calling the PosLemmaTaggerTests obj's underlying member method code with example usage: obj.test_empty_string() without return types