code: def test_mask_token(self):
      self.assertListEqual(
          self.tokenizer.convert_tokens_to_ids(["<mask>", "ar_AR"]),
          [256203, 3],
      )
  
imports: import shutil
  import tempfile
  import unittest
  from transformers import SPIECE_UNDERLINE, AddedToken, BatchEncoding, NllbTokenizer, NllbTokenizerFast, is_torch_available
  from transformers.testing_utils import get_tests_dir, nested_simplify, require_sentencepiece, require_tokenizers, require_torch
  from ...test_tokenization_common import TokenizerTesterMixin
label_desc: Use image node_id 6 for calling the NllbDistilledIntegrationTest obj's underlying member method code with example usage: obj.test_mask_token() without return types