This is the data saving in my rethinkdb database. And I save the data for 
`addtowatchlater` is array. I use ember.js for frontend and tornado for 
backend and database for rethinkdb.

```
{
    "accesstoken": "ajflasjjfasjfjasfasdfjasjflsajjfas" ,

    "addtowatchlater": [
        {
            "beatdescription":  "aa" ,
            "beatname":  "aa" ,
            "categoryname":  "DJ" ,
            "filename":  "asfasdfasdfasdfa" ,
            "id":  "423423454352342344545423434" ,
            "price":  "aa" ,
            "soldout":  "No" ,
            "stamp":  "1510244267000" ,
            "userid":  "816fbfe8-ea81-4198-98f0-5fb0db01e25e"
        },
        {
            "beatdescription":  "aa" ,
            "beatname":  "aa" ,
            "categoryname":  "DJ" ,
            "filename":  "asfasdfasdfasdfa" ,
            "id":  "423423454352342344545423434" ,
            "price":  "aa" ,
            "soldout":  "No" ,
            "stamp":  "1510244267000" ,
            "userid":  "816fbfe8-ea81-4198-98f0-5fb0db01e25e"}] ,

            "id":  "et4545er5454354354354353" ,

            "role":  "user" ,

            "status":  "Active" ,
        }

```

I want to remove one json data from `addtowatchlater` array field. When I 
remove I want like this for example.

```
{
    "accesstoken": "ajflasjjfasjfjasfasdfjasjflsajjfas" ,

    "addtowatchlater": [
        {
            "beatdescription": "aa" , 
            "beatname": "aa" , 
            "categoryname": "DJ" , 
            "filename": "asfasdfasdfasdfa" , 
            "id": "423423454352342344545423434" , 
            "price": "aa" , 
            "soldout": "No" , 
            "stamp": "1510244267000" , 
            "userid": "816fbfe8-ea81-4198-98f0-5fb0db01e25e"
        }
    ] ,

    "id": "et4545er5454354354354353" ,

    "role": "user" ,

    "status": "Active" , 
}

```