public void AddEnd(DateTime end, bool inclusive)
        {
            Contract.Requires(Find(end) != null);
            GexfTimePeriod current = Find(end);

            current.End          = end;
            current.EndInclusive = inclusive;
        }
        private GexfTimePeriod Find(DateTime dateTime)
        {
            GexfTimePeriod found = null;

            foreach (GexfTimePeriod spell in _spells)
            {
                if (spell.InRange(dateTime))
                {
                    found = spell;
                }
            }

            return(found);
        }