MongoDb Driver Fields Exclude

My problem is this, I have an object:

public class Obj(){
    prop int id {get; set;}
    prop Client client {get; set;}
}

public class Client(){
   prop int id {get; set;}
   prop Group group {get; set;}
}

public class Group(){
   prop int id {get; set;}
}

When doing the query, I would like to return only some values of the object:

var lRetorno = collection.Find(Query.And(query))
                .SetFields(Fields<Obj>.Include(c => c.id, c => c.Client)
                .Exclude(c => c.Client.Group))

Is there a way to return the obj Client without mapping the Group object, without changing the mapping of the class, including?