Mongo nested $graphLookup

I am trying to build discussion forum using MongoDB. I have data like this

 [
{
  "_id": "611c8a52d0de5860478ae7c7",
  "assetId": "611a50be0b8d8ea3dbe0f180",
  "comment": "First Comment",
  "parent": null
},
{
  "_id": "611c8a6bd0de5860478ae7c9",
  "assetId": "611a50be0b8d8ea3dbe0f180",
  "comment": "First-reply Comment",
  "parent": "611c8a52d0de5860478ae7c7"
},
{
  "_id": "611c8a7fd0de5860478ae7cb",
  "assetId": "611a50be0b8d8ea3dbe0f180",
  "comment": "First-reply reply Comment",
  "parent": "611c8a6bd0de5860478ae7c9"
}

]

where parent represents immediate comment/repy. I am expecting result as :

 [
{
  "_id": "611c8a52d0de5860478ae7c7",
  "assetId": "611a50be0b8d8ea3dbe0f180",
  "comment": "First Comment",
  "parent": null

  "reply": [
    {
      "_id": "611c8a6bd0de5860478ae7c9",
      "assetId": "611a50be0b8d8ea3dbe0f180",
      "comment": "First-reply Comment",
      "parent": "611c8a52d0de5860478ae7c7"

      reply: [
        {
          "_id": "611c8a7fd0de5860478ae7cb",
          "assetId": "611a50be0b8d8ea3dbe0f180",
          "comment": "First-reply reply Comment",
          "parent": "611c8a6bd0de5860478ae7c9",
        }
      ]
    }
  ]
}

]

I tried using $graphLookup but I am not getting result as expecting