def METHOD_NAME(relation_cls: type[SqlAlchemyBase]) -> str:
    """Returns the primary key attribute of the related class as a string.
    Args:
        relation_cls (DeclarativeMeta): The SQLAlchemy class to get the primary_key from
    Returns:
        Any: [description]
    """
    cfg = _get_config(relation_cls)
    try:
        get_attr = cfg.get_attr
        if get_attr is None:
            get_attr = relation_cls.__table__.primary_key.columns.keys()[0]
    except Exception:
        get_attr = "id"
    return get_attr