code: def test_create_vocabulary_single_token():
      data = pd.DataFrame(
          ["dog", "cat", "bird", "dog", "cat", "super cat"]
      )
      column = data[0]
  
      (
          vocab,
          str2idx,
          str2freq,
      ) = strings_utils.create_vocabulary_single_token(
          column,
          num_most_frequent=10000,
      )
  
      assert set(vocab) == {"dog", "cat", "bird", "super cat"}
      assert str2freq == {"dog": 2, "cat": 2, "bird": 1, "super cat": 1}
      assert strings_utils.UNKNOWN_SYMBOL not in str2idx
  
file_path: ludwig/tests/ludwig/utils/test_strings_utils.py
imports: from collections import defaultdict
  import numpy
  import pandas
  import pytest
  from ludwig.schema.features.preprocessing.text import TextPreprocessingConfig
  from ludwig.utils import strings_utils
label_desc: Use image node_id 9 for calling a global function with example usage: test_create_vocabulary_single_token() without return types