}

    @Override
    @CheckForNull
    public Range<C> get(@CheckForNull Object key) {
      if (key instanceof Cut) {
        try {
          @SuppressWarnings("unchecked") // we catch CCEs
          Cut<C> cut = (Cut<C>) key;
          if (!upperBoundWindow.contains(cut)) {
            return null;
          }
          Entry<Cut<C>, Range<C>> candidate = rangesByLowerBound.lowerEntry(cut);