to Array不是mongo数据库中的函数，mongoose，node.js

`getCartProducts: (userId) => {
        return new Promise(async (resolve, reject) => {
            let cart Items = await db.cart.aggregate([

                {`your text`
                    $match: { user: user Id }//matched with the id
                },
                {
                    $lookup: {
                        from: "db.products",
                        let: { proList: '$products' },
                        pipeline: [
                            {
                                $match: {
                                    $expr: {
                                        $in: ["$_id", '$$proList']
                                    }
                                }
                            }
                        ],
                        as: 'cart Items' //converted as cart Items name
                    }
                }

            ]).`to array`()
            resolve(`cart Items`)
        })
    }

db.cart.aggregate（）.to Array不是一个函数，我试图删除to数组，但它显示为未定义