code: def test_single_file_dir_vocab(self):
      with tempfile.TemporaryDirectory() as tempdir:
          sample_file = os.path.join(tempdir, "text.txt")
          with open(sample_file, "w", encoding="utf-8") as fout:
              fout.write(fake_text_1)
          vocab = char_model.build_charlm_vocab(tempdir)
  
      for i in fake_text_1:
          assert i in vocab
      assert "Q" not in vocab
  
imports: from collections import Counter
  import glob
  import lzma
  import os
  import tempfile
  import pytest
  from stanza.models import charlm
  from stanza.models.common import char_model
  from stanza.tests import TEST_MODELS_DIR
label_desc: Use image node_id 3 for calling the TestCharModel obj's underlying member method code with example usage: obj.test_single_file_dir_vocab() without return types