[代码]const res = await db.collection([代码][代码]'book_lend'[代码][代码]).where({[代码][代码]        [代码][代码]user: wxContext.OPENID[代码][代码]      [代码][代码]}).aggregate()[代码][代码]        [代码][代码].lookup({[代码][代码]          [代码][代码]from: [代码][代码]'books'[代码][代码],[代码][代码]          [代码][代码]localField: [代码][代码]'isbn'[代码][代码],[代码][代码]          [代码][代码]foreignField: [代码][代码]'isbn'[代码][代码],[代码][代码]          [代码][代码]as: [代码][代码]'bookDetail'[代码][代码],[代码][代码]        [代码][代码]})[代码][代码]        [代码][代码].end()[代码]以上代码会报错，‘collection().where().aggregate().lookup().end() is not a function ’,怎么写才对呢？