code: def apply_token_indexers(self, instance):
      instance.fields["line"].token_indexers = self._token_indexers
  
imports: from typing import Iterable
  import pytest
  from allennlp.common.testing import AllenNlpTestCase
  from allennlp.data.dataset_readers import DatasetReader, InterleavingDatasetReader
  from allennlp.data.data_loaders import MultiProcessDataLoader
  from allennlp.data.fields import TextField
  from allennlp.data.instance import Instance
  from allennlp.data.token_indexers import SingleIdTokenIndexer
  from allennlp.data.tokenizers import SpacyTokenizer
  from allennlp.data.vocabulary import Vocabulary
label_desc: Use image node_id 4 for calling the PlainTextReader obj's underlying member method code with example usage: obj.apply_token_indexers(instance) without return types