Mongo db multiple groupBy

mongoQuery.js

//given a set of documents
var db = [
  {
    "store": {
      "storeId": "1",
      "storeName: "A"
    },
    "audit": {
      "createdBy": "ME"
    }
  },
  {
    "store": {
      "storeId": "1",
      "storeName: "A"
    },
    "audit": {
      "createdBy": "YOU"
    }
  },
  {
    "store": {
      "storeId": "2",
      "storeName: "B"
    },
    "audit": {
      "createdBy": "YOU"
    }
  }
];

//and I want a mongo query to get all store ids that were created by ME and YOU
db.stores.aggregate([
{
    $group: {
        _id: {storeId: "$store.storeId", source: "$audit.createdBy"},
        count: { $sum: 1}
    }
},
{
    $group: {
        _id: "$_id.storeId",
        count: { $sum: 1}
    }
},
{
    $match: {
        count: { $gte: 2}
    }
}
]);