def clear_dag_task_instances():
    """
    
    """
    session = settings.Session()
    TI = TaskInstance
    tis = (
        session
        .query(TI)
        .filter(TI.dag_id.in_(DAG_IDS))
        .all()
    )
    for ti in tis:
        logging.info('Deleting TaskInstance :: {}'.format(ti))
        session.delete(ti)
    session.commit()