code: def test_get_timeline_plot(
      trial_states_list: list[TrialState],
  ) -> None:
      study = _create_study(trial_states_list)
      fig = plot_timeline(study)
      assert type(fig) is go.Figure
      fig.write_image(BytesIO())
  
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 6 for calling a global function with example usage: test_get_timeline_plot(trial_states_list) without return types