public void Remove(Dog dog) // L3 1.2
        {
            for (int i = 0; i < this.Count; i++)
            {
                if (this.dogs[i] == dog)
                {
                    for (int j = i; j < this.Count; j++)
                    {
                        this.dogs[j] = this.dogs[j + 1];
                    }
                }
            }
        }

        public void RemoveAt(int index) // L3 1.2
        {
            for (int i = 0; i < this.Count; i++)
            {
                if (i == index)
                {
                    for (int j = i; j < this.Count; j++)
                    {
                        this.dogs[j] = this.dogs[j + 1];
                    }
                }
            }
        }