code: def test_notebook_dir_exists() -> None:
      assert _NOTEBOOK_DIR.is_dir()
  
file_path: GPflow/tests/integration/test_notebooks.py
imports: import itertools
  import sys
  import traceback
  from pathlib import Path
  from typing import Sequence, Set
  import jupytext
  import nbformat
  import pytest
  from nbclient.exceptions import CellExecutionError
  from nbconvert.preprocessors.execute import ExecutePreprocessor
label_desc: Use image node_id 1 for calling a global function with example usage: test_notebook_dir_exists() without return types