code: def test_convert_tokens_to_string_format(self):
      # The default common tokenizer tests uses invalid tokens for Perceiver that can only accept one-character
      # strings and special added tokens as tokens
      tokenizers = self.get_tokenizers(fast=True, do_lower_case=True)
      for tokenizer in tokenizers:
          with self.subTest(f"{tokenizer.__class__.__name__}"):
              tokens = [
                  "[CLS]",
                  "t",
                  "h",
                  "i",
                  "s",
                  " ",
                  "i",
                  "s",
                  " ",
                  "a",
                  " ",
                  "t",
                  "e",
                  "s",
                  "t",
                  "[SEP]",
              ]
              string = tokenizer.convert_tokens_to_string(tokens)
  
              self.assertIsInstance(string, str)
  
imports: import json
  import os
  import re
  import shutil
  import tempfile
  import unittest
  from typing import Tuple
  from transformers import AddedToken, BatchEncoding, PerceiverTokenizer
  from transformers.utils import cached_property, is_tf_available, is_torch_available
  from ...test_tokenization_common import TokenizerTesterMixin
label_desc: Use image node_id 16 for calling the PerceiverTokenizationTest obj's underlying member method code with example usage: obj.test_convert_tokens_to_string_format() without return types