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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def by_user_and_perm(cls, user_id, perm_name, db_session=None):
 """ return by user and permission name :param user_id: :param perm_name: :param db_session: :return: """

        db_session = get_db_session(db_session)
        query = db_session.query(cls.model).filter(cls.model.user_id == user_id)
        query = query.filter(cls.model.perm_name == perm_name)
        return query.first()