code: def test_filenames_from_a_single_file():
      """Verify that we simply yield that filename."""
      filenames = set(
          _filenames_from(_normpath("a/b/c.py"), predicate=_noop)
      )
      assert filenames == {_normpath("a/b/c.py")}
  
imports: from __future__ import annotations
  import os.path
  import pytest
  from flake8 import utils
  from flake8.discover_files import _filenames_from
  from flake8.discover_files import expand_paths
label_desc: Use image node_id 8 for calling a global function with example usage: test_filenames_from_a_single_file() without return types