code: def test_datetime_start(storage_mode: str) -> None:
      trial_datetime_start: List[Optional[datetime.datetime]] = [None]
  
      def objective(trial: Trial) -> float:
          trial_datetime_start[0] = trial.datetime_start
          return 1.0
  
      with StorageSupplier(storage_mode) as storage:
          study = create_study(storage=storage)
          study.optimize(objective, n_trials=1)
  
          assert (
              study.trials[0].datetime_start == trial_datetime_start[0]
          )
  
imports: from __future__ import annotations
  import datetime
  import math
  from typing import Any
  from typing import Dict
  from typing import List
  from typing import Optional
  from typing import Tuple
  from unittest.mock import Mock
  from unittest.mock import patch
  import warnings
  import numpy
  import pytest
  import optuna
  from optuna import create_study
  from optuna import distributions
  from optuna import load_study
  from optuna import samplers
  from optuna import storages
  from optuna.distributions import CategoricalDistribution
  from optuna.distributions import FloatDistribution
  from optuna.distributions import IntDistribution
  from optuna.testing.pruners import DeterministicPruner
  from optuna.testing.samplers import DeterministicSampler
  from optuna.testing.storages import STORAGE_MODES
  from optuna.testing.storages import StorageSupplier
  from optuna.testing.tempfile_pool import NamedTemporaryFilePool
  from optuna.trial import Trial
  from optuna.trial._trial import _LazyTrialSystemAttrs
label_desc: Use image node_id 21 for calling a global function with example usage: test_datetime_start(storage_mode) and returns: int