return null;
          } else if (cut.equals(restriction.lowerBound)) {
            // it might be present, truncated on the left
            Range<C> candidate = Maps.valueOrNull(rangesByLowerBound.floorEntry(cut));
            if (candidate != null && candidate.upperBound.compareTo(restriction.lowerBound) > 0) {
              return candidate.intersection(restriction);
            }