docs: public int sizeInSequence() {
          int sequence = 0;
          if (m_map.isEmpty()) {
              return sequence;
          }
          final Iterator<Range<Long>> iter = m_map.asRanges().iterator();
          while (iter.hasNext()) {
              Range<Long> range = iter.next();
              sequence += end(range) - start(range) + 1;
          }
          if (m_hasSentinel) {
              sequence -= 1;
          }
          return sequence;
      }