code: def test_study_direction_best_value(
      client: "Client", direction: str
  ) -> None:
      # Regression test for https://github.com/jrbourbeau/dask-optuna/issues/15
      pytest.importorskip("pandas")
      storage = DaskStorage()
      study = optuna.create_study(storage=storage, direction=direction)
      f = client.submit(study.optimize, objective, n_trials=10)  # type: ignore[no-untyped-call]
      wait(f)  # type: ignore[no-untyped-call]
  
      # Ensure that study.best_value matches up with the expected value from
      # the trials DataFrame
      trials_value = study.trials_dataframe()["value"]
      if direction == "maximize":
          expected = trials_value.max()
      else:
          expected = trials_value.min()
  
      np.testing.assert_allclose(expected, study.best_value)
  
imports: from contextlib import contextmanager
  import time
  from typing import Iterator
  import numpy
  import pytest
  import optuna
  from optuna._imports import try_import
  from optuna.integration.dask import _OptunaSchedulerExtension
  from optuna.integration.dask import DaskStorage
  from optuna.testing.tempfile_pool import NamedTemporaryFilePool
  from optuna.trial import Trial
label_desc: Use image node_id 10 for calling a global function with example usage: test_study_direction_best_value(client, direction) without return types