code: def test_cascade_delete_on_study(session: Session) -> None:
      directions = [
          StudyDirectionModel(
              study_id=1, direction=StudyDirection.MINIMIZE, objective=0
          ),
          StudyDirectionModel(
              study_id=1, direction=StudyDirection.MAXIMIZE, objective=1
          ),
      ]
      study = StudyModel(
          study_id=1, study_name="test-study", directions=directions
      )
      session.add(study)
      session.commit()
  
      assert 2 == len(
          StudyDirectionModel.where_study_id(study.study_id, session)
      )
  
      session.delete(study)
      session.commit()
  
      assert 0 == len(
          StudyDirectionModel.where_study_id(study.study_id, session)
      )
  
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 3 for calling the TestStudyDirectionModel obj's underlying member method code with example usage: obj.test_cascade_delete_on_study(session) without return types