code: def test_get_timeline_info_empty() -> None:
      study = optuna.create_study()
      info = _get_timeline_info(study)
      assert len(info.bars) == 0
  
file_path: optuna/tests/visualization_tests/test_timeline.py
imports: from __future__ import annotations
  import datetime
  from io import BytesIO
  from typing import Any
  import _pytest.capture
  import pytest
  import optuna
  from optuna.samplers._base import _CONSTRAINTS_KEY
  from optuna.study.study import Study
  from optuna.trial import TrialState
  from optuna.visualization._plotly_imports import go
  from optuna.visualization._timeline import _get_timeline_info
  from optuna.visualization._timeline import plot_timeline
label_desc: Use image node_id 3 for calling a global function with example usage: test_get_timeline_info_empty() without return types