code: def test_cascade_delete_on_study(session: Session) -> None:
      study_id = 1
      direction = StudyDirectionModel(
          direction=StudyDirection.MINIMIZE, objective=0
      )
      study = StudyModel(
          study_id=study_id,
          study_name="test-study",
          directions=[direction],
      )
      study.trials.append(
          TrialModel(study_id=study.study_id, state=TrialState.COMPLETE)
      )
      study.trials.append(
          TrialModel(study_id=study.study_id, state=TrialState.RUNNING)
      )
      session.add(study)
      session.commit()
  
      assert 2 == TrialModel.count(session, study)
  
      session.delete(study)
      session.commit()
  
      assert 0 == TrialModel.count(session, study)
  
imports: from datetime import datetime
  import pytest
  from sqlalchemy import create_engine
  from sqlalchemy.exc import IntegrityError
  from sqlalchemy.orm import Session
  from optuna.storages._rdb.models import BaseModel
  from optuna.storages._rdb.models import StudyDirectionModel
  from optuna.storages._rdb.models import StudyModel
  from optuna.storages._rdb.models import StudySystemAttributeModel
  from optuna.storages._rdb.models import TrialHeartbeatModel
  from optuna.storages._rdb.models import TrialIntermediateValueModel
  from optuna.storages._rdb.models import TrialModel
  from optuna.storages._rdb.models import TrialSystemAttributeModel
  from optuna.storages._rdb.models import TrialUserAttributeModel
  from optuna.storages._rdb.models import TrialValueModel
  from optuna.storages._rdb.models import VersionInfoModel
  from optuna.study._study_direction import StudyDirection
  from optuna.trial import TrialState
label_desc: Use image node_id 4 for calling the TestTrialModel obj's underlying member method code with example usage: obj.test_cascade_delete_on_study(session) without return types