/// <inheritdoc />
        public void Unsubscribe(ITickerSubscriber subscriber)
        {
            Preconditions.CheckNotNull(subscriber);

            // Unsubscribe subscriber
            lock (_subscribers)
            {
                _subscribers.Remove(subscriber);
            }
        }
        /// <inheritdoc />
        public void Subscribe(ITickerSubscriber subscriber)
        {
            Preconditions.CheckNotNull(subscriber);

            // Subscribe subscriber
            lock (_subscribers)
            {
                _subscribers.Add(subscriber);
            }
        }