Mongoose 聚合：无法使用查找填充 2 级嵌套字段

如何解决Mongoose 聚合：无法使用查找填充 2 级嵌套字段

我有三个模型 Institution、User 和 Profile

机构

const InstitutionSchema = new Schema({
  current_students: [
    {
      type: Schema.Types.ObjectId,ref: "users",},],});

用户

const UserSchema = new Schema({
  name: {
    type: Schema.Types.String,profile: {
    type: Schema.Types.ObjectId,ref: "profiles",});

简介

const ProfileSchema = new Schema({
      videoURL: {
        type: Schema.Types.String,});

我正在尝试取回机构数组并填充 current_students.user 和 current_students.user.profile：

Institution.aggregate([
    {
      $lookup: {
        from: "users",localField: "current_students",foreignField: "_id",as: "current_students",{
      $unwind: {
        path: "$current_students",{
      $lookup: {
        from: "profiles",localField: "current_students._id",foreignField: "profile",as: "current_students.profile",]);

但是，这总是将配置文件字段返回为空。