public static IEnumerable <KeyValuePair <object, uint> > Frequencies(this System.Collections.ArrayList x)
        {
            Dictionary <object, uint> frequencies = x.FrequencyCounter();

            IEnumerable <KeyValuePair <object, uint> > frequencies_sorted =
                from pair in frequencies
                orderby pair.Value descending
                select pair
            ;

            return(frequencies_sorted);
        }