/// <summary>
        /// Compare the delays of two messages.
        /// </summary>
        /// <param name="o"> Delayed messages.</param>
        /// <returns> Returns the result. 0 if equal, -1 if o has smaller delay, 1 if o has larger delay.</returns>
        public override int CompareTo(Delayed o)
        {
            double a = o.GetDelay();
            double b = this.GetDelay();

            if (a < b)
            {
                return(-1);
            }
            else if (a > b)
            {
                return(1);
            }
            else
            {
                return(0);
            }
        }
        /// <summary>
        /// Compare the delays of two messages.
        /// </summary>
        /// <param name="o"> Delayed messages.</param>
        /// <returns> Returns the result. 0 if equal, -1 if o has smaller delay, 1 if o has larger delay.</returns>
        public override int CompareTo(Delayed o)
        {
            double a = o.GetDelay();
            double b = this.GetDelay();

            if (a < b)
            {
                return -1;
            }
            else if (a > b)
            {
                return 1;
            }
            else
            {
                return 0;
            }
        }