public List<Model> GetModels()
        {
            var models = new List<Model>();

            foreach (Actor actor in registeredActors.Where(n=>n is ImplementsGraphics))
            {
                var graphicActor = (ImplementsGraphics)actor;
                models.AddRange(graphicActor.GetModels());
            }
            return models;
        }

public List<Model> GetModels()
        {
            var models = new List<Model>();

            foreach (Actor actor in registeredActors)
            {
                if((ImplementsGraphics)actor != null)
                    models.AddRange(((ImplementsGraphics)actor).GetModels());
            }
            return models;
        }