docs: private void extractSequenceNumber() {
          if (this.sequenceNumber == -1) {
              final int seqNum = payload.getUnsignedByte(HEADER_PART_SEQNUM_START);
              if (seqNum >= 0) {
                  this.sequenceNumber = seqNum;
              } else {
                  throw new IllegalStateException("Could not extract sequence number");
              }
          }
      }