code: def test_elmo_indexer_with_additional_tokens(self):
      indexer = ELMoTokenCharactersIndexer(tokens_to_add={"<first>": 1})
      tokens = [Token("<first>")]
      indices = indexer.tokens_to_indices(tokens, Vocabulary())
      expected_indices = [
          [
              259,
              2,
              260,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
              261,
          ]
      ]
      assert indices["elmo_tokens"] == expected_indices
  
file_path: allennlp/tests/data/token_indexers/elmo_indexer_test.py
imports: import numpy
  import pytest
  from allennlp.common.testing import AllenNlpTestCase
  from allennlp.data import Token, Vocabulary, Instance
  from allennlp.data.batch import Batch
  from allennlp.data.token_indexers import ELMoTokenCharactersIndexer
  from allennlp.data.fields import ListField, TextField
label_desc: Use image node_id 5 for calling the TestELMoTokenCharactersIndexer obj's underlying member method code with example usage: obj.test_elmo_indexer_with_additional_tokens() without return types