Aggregation unwind multiple arrays $lookup as multiple fields for projection - mongodb

Question

This is my current query:
Follow.aggregate([
{
$match: {
"user": Types.ObjectId(user_id)
}
},
{
$unwind: "$following"
},
{
$lookup: {
"from": "users",
"localField": "following",
"foreignField": "createdById",
"as": "followingUsers"
}
}, {
$project: {
"user": 1,
"followingUsers": 1
}
}
])
This query is run on a document like this:
{
"_id" : ObjectId("5a271a93a19d690b25a3e181"),
"user" : ObjectId("5a271a4f50261a3c1695a391"),
"following" : [
ObjectId("5a257c87086eb00712fd02ec"),
ObjectId("5a257a79086eb00712fd02eb")
],
"followers" : [
ObjectId("5a257a79086eb00712fd02eb")
]
}
And gives a result like this:
{
"_id" : ObjectId("5a271a93a19d690b25a3e181"),
"user" : ObjectId("5a271a4f50261a3c1695a391"),
"followingUsers" : [
{
"_id" : ObjectId("5a257a79086eb00712fd02eb"),
"email" : "email#gmail.com",
"username" : "username",
"email_verified" : true,
"created" : ISODate("2010-12-04T16:40:25.670Z"),
"__v" : 0,
"last_login" : ISODate("2010-12-06T21:14:25.538Z"),
"is_active" : false
}
]
}
The above unwinds only one of the arrays and follows up the lookup.
I want to, in one scoop (assuming that is possible)
unwind both the $following and $followers array fields
$lookup both of the array fields independently
then have both come out as, say, followingUsers and followersUsers
So end up with something like this:
{
"_id" : ObjectId("5a271a93a19d690b25a3e181"),
"user" : ObjectId("5a271a4f50261a3c1695a391"),
"followingUsers" : [
{
"_id" : ObjectId("5a257a79086eb00712fd02eb"),
....
}
],
"followersUsers": [
{
"_id" : ObjectId("5a257a79086eb00712fd02eb"),
....
}
]
}
Am I even sane to imagine something like this in MongoDB?