code: def test_pickle(self):
      tokenizer = GPT2Tokenizer.load(
          self.tmp_dir.name, self.special_tokens_map
      )
      self.assertIsNotNone(tokenizer)
  
      text = "Munich and Berlin are nice cities"
      subwords = tokenizer.map_text_to_token(text)
  
      with tempfile.TemporaryDirectory() as tmpdirname:
          filename = os.path.join(tmpdirname, "tokenizer.bin")
          with open(filename, "wb") as f:
              pickle.dump(tokenizer, f)
          with open(filename, "rb") as f:
              tokenizer_new = pickle.load(f)
  
      subwords_loaded = tokenizer_new.map_text_to_token(text)
  
      self.assertListEqual(subwords, subwords_loaded)
  
file_path: texar/tests/data/tokenizers/gpt2_tokenizer_test.py
imports: import json
  import os
  import pickle
  import tempfile
  import tensorflow
  from texar.tf.data.tokenizers.gpt2_tokenizer import GPT2Tokenizer
  from texar.tf.utils.test import pretrained_test
label_desc: Use image node_id 5 for calling the GPT2TokenizerTest obj's underlying member method code with example usage: obj.test_pickle() without return types