在猫鼬中使用聚集来填充参考对象的数组

Question

[{
_id:5c89eb0a81c2b63df5953559
customer_email:"sakshi@gmail.com"
customer_phone:"678899999999"
birthday_date:2019-02-12 00:00:00.000
anniversary_date:2019-02-27 00:00:00.000
tags:["5c89eb0a81c2b63df5953579","5c89eb0a81c2b63df5953578"]
customer_name:"sakshimini"
source_type:"TableBooking"
userId:5c2d8ed5dd20394519f823aa
createdAt:2019-03-14 05:47:54.379
gender:"Male"
}]

我尝试返回猫鼬聚合并沿着联系人填充标签。但它返回空数组。我期待标签的对象数组。