Q: Mongoose populate data key remove in got data I'm using relation between two collection and I have collection schema like follow.
// Room database Entry.
{
    "_id" : ObjectId("59b77082f7da4b1b3f64d927"),
    "room_id" : "c3wqqkfndg9cnmi",
    "room_name" : "bcmvnxbcnvsjkfhkjdh",
    "users" : [
        {
            "_id" : ObjectId("59b77082f7da4b1b3f64d926")
        }
    ],
    "__v" : 0
}

//User Database Entry, Related with above Room entry.
{
    "_id" : ObjectId("59b77082f7da4b1b3f64d926"),
    "user_id" : "dyr1qlrtso47vi",

    "__v" : 0
}

When I pass query for Room Find and populate the data than I found result like follow.
// Query For Room find and Populate.
room
 .findOne({ room_id: result.data.room_id })
 .populate("users._id")
 .exec(function(err, data){
  });

//Result As Follow
{
   "_id":"59b77082f7da4b1b3f64d927",
   "room_id":"c3wqqkfndg9cnmi",
   "room_name":"bcmvnxbcnvsjkfhkjdh",
   "__v":0,
   "users":[
      {
         "_id":{
            "_id":"59b77082f7da4b1b3f64d926",
            "user_id":"dyr1qlrtso47vi",
            "__v":0
         }
      }
   ]
}

My Requirement is like follow, I don't want _id as key of object. I need users object like follow.
"users":[
      {
         "_id":{
            "_id":"59b77082f7da4b1b3f64d926",
            "user_id":"dyr1qlrtso47vi",
            "__v":0
         }
      }
   ]

Should be 

"users":[
         {
            "_id":"59b77082f7da4b1b3f64d926",
            "user_id":"dyr1qlrtso47vi",
            "__v":0
         }
     ]

