code: def test_index_to_tokens(self, tokens):
      # decoder tokens: '-' '|' 'f' 'o' 'b' 'a' 'r'
      decoder = self._get_decoder(tokens)
  
      idxs = torch.LongTensor((1, 2, 1, 3, 5))
      tokens = decoder.idxs_to_tokens(idxs)
  
      expected_tokens = ["|", "f", "|", "o", "a"]
      self.assertEqual(tokens, expected_tokens)
  
imports: import itertools
  import torch
  from parameterized import parameterized
  from torchaudio_unittest.common_utils import get_asset_path, skipIfNoCtcDecoder, TempDirMixin, TorchaudioTestCase
label_desc: Use image node_id 13 for calling the CTCDecoderTest obj's underlying member method code with example usage: obj.test_index_to_tokens(tokens) without return types