Add custom section to a resource

Hi,

I'm using Fractal for my api. I'm trying to include a custom section on my response that would be appended to my collection and give me some stats about the response.

An example : If I'm getting messages, I currently get a response with messages and pagination, great... But I can't figure out is how to append a customized section that would give stats about my messages (read, latest...).

To get something like that :

{ 
"messages" : [ {...}, {...}, ....],
"pagination": {...},
"stats": {
        "unread" : 3,
        "whatever": 5,
    }
}

Do you have any idea on how to handle that ??

Thanks !