public MostCommonSubsets(TimeSpan window)
        {
            _window         = window;
            _counterSubsets = new SortedDictionary <int, ISet <SubsetInfo> >();
            _datetimeSubset = new SortedDictionary <DateTime, SubsetInfo>();
            KeySetComparer <string> comparer = new KeySetComparer <string>();

            _keySetSubset = new Dictionary <KeySet <string>, SubsetInfo>(comparer);
        }
 public KeySetDictionary()
 {
     _comparer          = new KeySetComparer <T>();
     _keySetToDocuments = new Dictionary <int, ISet <U> >();
 }