code: def test_number() -> None:
      study = optuna.multi_objective.create_study(
          ["maximize", "minimize", "maximize"]
      )
  
      def objective(
          trial: optuna.multi_objective.trial.MultiObjectiveTrial,
          number: int,
      ) -> List[float]:
          assert trial.number == number
          return [0, 0, 0]
  
      for i in range(10):
          study.optimize(lambda t: objective(t, i), n_trials=1)
  
      for i, trial in enumerate(study.trials):
          assert trial.number == i
  
file_path: optuna/tests/multi_objective_tests/test_trial.py
imports: from __future__ import annotations
  import datetime
  from typing import List
  from typing import Tuple
  import pytest
  import optuna
  from optuna.multi_objective.trial import FrozenMultiObjectiveTrial
  from optuna.study._study_direction import StudyDirection
  from optuna.trial import TrialState
label_desc: Use image node_id 3 for calling a global function with example usage: test_number() and returns: list