`pytorch` and `visualization` examples do not work

[c-bata]

Expected behavior

pytorch and visualization examples fail to run because they depend on OpenML datasets that have been unavailable for a long time.

• pytorch : https://github.com/optuna/optuna-examples/actions/runs/18656229358
  • sklearn.datasets._openml.OpenMLError: No active dataset mnist_784 found.
• visualization : https://github.com/optuna/optuna-examples/actions/runs/18656184541/job/53185765384
  • sklearn.datasets._openml.OpenMLError: Dataset fashion-mnist with version 1 not found.

Environment

Please refer to CI logs for details.

Error messages, stack traces, or logs

Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/optuna/study/_optimize.py", line 205, in _run_trial
    value_or_values = func(trial)
  File "/home/runner/work/optuna-examples/optuna-examples/visualization/plot_study.py", line 38, in objective
    fmnist = fetch_openml(name="Fashion-MNIST", version=1)
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/sklearn/utils/_param_validation.py", line 216, in wrapper
    return func(*args, **kwargs)
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/sklearn/datasets/_openml.py", line 1011, in fetch_openml
    data_info = _get_data_info_by_name(
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/sklearn/datasets/_openml.py", line 343, in _get_data_info_by_name
    json_data = _get_json_content_from_openml_api(
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/sklearn/datasets/_openml.py", line 254, in _get_json_content_from_openml_api
    raise OpenMLError(error_message)
sklearn.datasets._openml.OpenMLError: Dataset fashion-mnist with version 1 not found.
[W 2025-10-20 15:02:33,433] Trial 0 failed with value None.
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/sklearn/datasets/_openml.py", line 329, in _get_data_info_by_name
    json_data = _get_json_content_from_openml_api(
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/sklearn/datasets/_openml.py", line 254, in _get_json_content_from_openml_api
    raise OpenMLError(error_message)
sklearn.datasets._openml.OpenMLError: None

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/runner/work/optuna-examples/optuna-examples/visualization/plot_study.py", line 71, in <module>
    study.optimize(objective, n_trials=100, timeout=600)
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/optuna/study/study.py", line 490, in optimize
    _optimize(
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/optuna/study/_optimize.py", line 67, in _optimize
    _optimize_sequential(
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/optuna/study/_optimize.py", line 164, in _optimize_sequential
    frozen_trial_id = _run_trial(study, func, catch)
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/optuna/study/_optimize.py", line 262, in _run_trial
    raise func_err
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/optuna/study/_optimize.py", line 205, in _run_trial
    value_or_values = func(trial)
  File "/home/runner/work/optuna-examples/optuna-examples/visualization/plot_study.py", line 38, in objective
    fmnist = fetch_openml(name="Fashion-MNIST", version=1)
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/sklearn/utils/_param_validation.py", line 216, in wrapper
    return func(*args, **kwargs)
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/sklearn/datasets/_openml.py", line 1011, in fetch_openml
    data_info = _get_data_info_by_name(
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/sklearn/datasets/_openml.py", line 343, in _get_data_info_by_name
    json_data = _get_json_content_from_openml_api(
  File "/opt/hostedtoolcache/Python/3.9.24/x64/lib/python3.9/site-packages/sklearn/datasets/_openml.py", line 254, in _get_json_content_from_openml_api
    raise OpenMLError(error_message)
sklearn.datasets._openml.OpenMLError: Dataset fashion-mnist with version 1 not found.```

Steps to reproduce

Please refer to workflow files

• https://github.com/optuna/optuna-examples/blob/main/.github/workflows/pytorch.yml
• https://github.com/optuna/optuna-examples/blob/main/.github/workflows/visualization.yml

[github-actions]

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