How does serializing work

I am trying to fetch a object that I got from mongodb, but when doing


return json(object, {
            status: 200
        })


return json(object, {
            status: 200
        })

and then


        const response = await get_user(prof_id);
        const data = await response.json()


        const response = await get_user(prof_id);
        const data = await response.json()

The following error is logged "The value [object Object] of type "object" cannot be parsed/serialized."

How does serializing work - SolidJS