Nested data in flask endpoint response

Question

I have following tables:

Contributor:
- id
- user_id
- project_id

User:
- id
- full_name
- username

Project:
- id
- name

and I need to get list of all contributors in given project:

what i have so far in my endpoint code:

contributors = session.query(Contributor).filter_by(project_id=project_id).all()
return to_json(contributors)

implementation of to_json method:

def to_json(result: Any) -> str:
    return flask.jsonify(_convert_models(result))

and json method in Contributor model:

def __json__(self):
    return ('id', 'user_id', 'project_id')

this would give me following response:

[
    {
        "id": 1,
        "project_id": 1,
        "user_id": 1
    },
    {
        "id": 2,
        "project_id": 1,
        "user_id": 2
    }
]

what I need is something like that:

[
    {
        "id": 1,
        "project_id": 1,
        "user": {
            "id": 1,
            "full_name": "Darth Vader",
        }
    },
    ...
]