{
    "_id" : ObjectId("58ca3a856d13601f9a474dca"),
    "name" : "user A",
    "email" : "userA@gmail.com",
    "transaction" : [
        {
            "amount" : 50,
            "type" : "CASH"
        }
    ]
}

{
    "_id" : ObjectId("58ca3a856d13601f9a474dcb"),
    "name" : "user B",
    "email" : "userB@gmail.com",
    "transaction" : [
        {
            "amount" : 100,
            "type" : "CHEQUE"
        },
        {
            "amount" : 200,
            "type" : "CASH"
        },
        {
            "amount" : -20,
            "type" : "USED_SERVICE"
        }
    ]
}

{
    "_id" : ObjectId("58ca3a856d13601f9a474dcc"),
    "name" : "user C",
    "email" : "userC@gmail.com",
    "transaction" : [
        {
            "amount" : 20,
            "type" : "CASH"
        },
        {
            "amount" : -5,
            "type" : "USED_SERVICE"
        }
    ]
}