public static SortList instance(IDataSeries input, int period)
 {
     if (input == null)
     {
         return(new SortList(input, period));
     }
     lock (dict) {
         key k = new key(input, period);
         if (dict.ContainsKey(k))
         {
             return(dict[k]);
         }
         else
         {
             return(dict[k] = new SortList(input, period));
         }
     }
 }
		public static SortList instance(IDataSeries input, int period)
		{
			if ( input == null )
				return new SortList(input, period);
			lock(dict) {
				key k = new key(input, period);
				if ( dict.ContainsKey(k) )
					return dict[k];
				else
					return dict[k] = new SortList(input, period);
			}
		}