public IFlockCollection DestroyFlock(HashSet <IFlockBoid> flock)
        {
            if (Flocks.Contains(flock))
            {
                Flocks.Remove(flock);
            }

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

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

            return(this);
        }