code: def test_num_classes(self):
      with tempfile.TemporaryDirectory() as tmp_dir:
          # create dummy data
          dict_file = osp.join(tmp_dir, "fake_chars.txt")
          create_dummy_dict_file(dict_file)
          dict_gen = Dictionary(dict_file=dict_file)
          assert dict_gen.num_classes == 36
  
file_path: mmocr/tests/test_models/test_textrecog/test_dictionary/test_dictionary.py
imports: import os.path
  import tempfile
  from unittest import TestCase
  from mmocr.models.common import Dictionary
  from mmocr.testing import create_dummy_dict_file
label_desc: Use image node_id 2 for calling the TestDictionary obj's underlying member method code with example usage: obj.test_num_classes() without return types