public ISet <string> GetAccreditedSetSymmetricExceptResult(ISet <string> first, ISet <string> second)
            {
                if (first == null)
                {
                    throw new ArgumentNullException(nameof(first));
                }
                if (second == null)
                {
                    throw new ArgumentNullException(nameof(second));
                }

                RangeSet <string> set = new RangeSet <string>(this.rangeInfo);

                set.UnionWith(first);
                set.SymmetricExceptWith(second);
                return(set);
            }