code: def test_string_tokenizer(self) -> None:
      sentence = "Hello there"
      tokenizer = CharTokenizer()
      assert tokenizer.tokenize(sentence) == list(sentence)
      assert list(tokenizer.span_tokenize(sentence)) == [
          (0, 1),
          (1, 2),
          (2, 3),
          (3, 4),
          (4, 5),
          (5, 6),
          (6, 7),
          (7, 8),
          (8, 9),
          (9, 10),
          (10, 11),
      ]
  
imports: from typing import List, Tuple
  import pytest
  from nltk.tokenize import LegalitySyllableTokenizer, StanfordSegmenter, SyllableTokenizer, TreebankWordTokenizer, TweetTokenizer, punkt, sent_tokenize, word_tokenize
  from nltk.tokenize.simple import CharTokenizer
label_desc: Use image node_id 23 for calling the TestTokenize obj's underlying member method code with example usage: obj.test_string_tokenizer() without return types