Измените структуру данных поискового запроса MongoDB $

{
    "_id" : ObjectId("5b74f57d3eb9591fcc069406"),
    "received_by" : ObjectId("5b6bac617e9f754ff8aebd65"),
    "received_date" : "2019",
    "code" : "TRSV16081800007",
    "items" : [ 
        {
            "m_souvenir_id" : ObjectId("5b70e98ccb72df3bec00c94a"),
            "qty" : "10"
        },
         {
            "m_souvenir_id" : ObjectId("5b70e98ccb72df3bec00c94a"),
            "qty" : "10"
        },
        
        
    ]
}

{
    "_id" : ObjectId("5b74f57d3eb9591fcc069406"),
    "received_by" : ObjectId("5b6bac617e9f754ff8aebd65"),
    "received_date" : "2019",
    "code" : "TRSV16081800007",
    "items" : [ 
        {
            "m_souvenir_id" : ObjectId("5b70e98ccb72df3bec00c94a"),
            "qty" : "10"
        }
    ]
}

/* 2 */
{
    "_id" : ObjectId("5b74f57d3eb9591fcc069406"),
    "received_by" : ObjectId("5b6bac617e9f754ff8aebd65"),
    "received_date" : "2019",
    "code" : "TRSV16081800007",
    "items" : [ 
        {
            "m_souvenir_id" : ObjectId("5b70e9d7cb72df3bec00c94b"),
            "qty" : "20"
        }
    ]
}

db.t_souvenir.aggregate([
	{ $lookup: { from: "t_souvenir_item", localField:"_id", foreignField:"t_souvenir_id", as: "Items"}},
        { $unwind : "$Items" },
	{ $project : {
	  		"code":1,
	  		"received_by":1,
	  		"received_date":1,
                        items : {
	  		"m_souvenir_id":"$Items.m_souvenir_id",
                        "qty":"$Items.qty",
                        },
	  		
	}};**strong text**

]);