SampleJSON_FB

```json
users = [
    
        {
            "_id" : 1000,
            "fb_id" : "a",
            "username" : "",
            /* user other fields */
            "posts" : [
                {
                    "_id" : 2000,
                    "fb_id" : "b",
                    /* post fields */     
                },
                {
                    "_id" : 2001,
                    "fb_id" : "c",
                    /* post fields */     
                }
            ]
        },
        {
            "_id" : 1001,
            "fb_id" : "e",
            "username" : "",
            /* user other fields */
            "posts" : [
                {
                    "_id" : 3001,
                    "fb_id" : "f",
                    /* post fields */     
                },
                {
                    "_id" : 3002,
                    "fb_id" : "x",
                    /* post fields */     
                }
            ]
        },
]
```