docs: private void writeObject(ObjectOutputStream out) throws IOException {
          out.writeLong(m_lastSpUniqueId);
          out.writeLong(m_lastMpUniqueId);
          out.writeShort(m_producerPartitionId);
          out.writeInt(m_map.asRanges().size());
          for(Range<Long> entry : m_map.asRanges()) {
              out.writeLong(start(entry));
              out.writeLong(end(entry));
          }
      }