[{"key":"5d4eee8047206b6d2df212bb"},]

db.collection.aggregate([{$match:{key:{$in:["5d4eee8047206b6d2df212bb","5d4eee8047206b6d2df212bb","5d4eee8047206b6d2df212bb"]}}},{"$addFields":{"itemsArray":["5d4eee8047206b6d2df212bb","5d4eee8047206b6d2df212bb","5d4eee8047206b6d2df212bb"]}},{"$unwind":"$itemsArray"},])