code: def test_empty() -> None:
      source = expected = ""
      assert_format(source, expected)
  
file_path: black/tests/test_format.py
imports: from dataclasses import replace
  from typing import Any, Iterator
  from unittest.mock import patch
  import pytest
  import black
  from black.mode import TargetVersion
  from tests.util import all_data_cases, assert_format, dump_to_stderr, read_data, read_data_with_mode
label_desc: Use image node_id 5 for calling a global function with example usage: test_empty() without return types