public IFlockCollection AddBoid(HashSet <IFlockBoid> flock, IFlockBoid boid)
        {
            flock.Add(boid);

            if (!Flocks.Contains(flock))
            {
                Flocks.Add(flock);
            }

            return(this);
        }
        public IFlockCollection CreateFlock(IEnumerable <IFlockBoid> boids)
        {
            Flocks.Add(new HashSet <IFlockBoid>(boids));

            return(this);
        }