code: def test_space(self):
      # for example, character models treat space as a symbol
      dict_file = io.StringIO("  999\n" "a 999\n" "b 999\n")
      d = Dictionary()
      d.add_from_file(dict_file)
      self.assertEqual(d.index(" "), 4)
      self.assertEqual(d.index("a"), 5)
      self.assertEqual(d.index("b"), 6)
  
file_path: fairseq/tests/test_dictionary.py
imports: import io
  import os
  import string
  import tempfile
  import unittest
  import torch
  from fairseq import tokenizer
  from fairseq.data import Dictionary
label_desc: Use image node_id 4 for calling the TestDictionary obj's underlying member method code with example usage: obj.test_space() without return types