code: def test_add_special_tokens(self, test_data_dir):
      tokenizer = SentencePieceTokenizer(
          test_data_dir + self.model_name, legacy=True
      )
      special_tokens = MODEL_SPECIAL_TOKENS
      tokenizer.add_special_tokens(special_tokens)
      assert (
          tokenizer.vocab_size
          == tokenizer.original_vocab_size
          + len(set(special_tokens.values()))
      )
  
imports: import pytest
  from nemo.collections.common.tokenizers.sentencepiece_tokenizer import SentencePieceTokenizer
  from nemo.collections.common.tokenizers.youtokentome_tokenizer import YouTokenToMeTokenizer
label_desc: Use image node_id 1 for calling the TestSentencePieceTokenizerLegacy obj's underlying member method code with example usage: obj.test_add_special_tokens(test_data_dir) without return types