code: public byte[] toBytes()
      {
          if (tc.isEntryEnabled()) Tr.entry(tc, "toBytes");
  
          final byte[] result = new byte[16];
  
          final int t1 = (int)(_timestamp >> 32 & 0xFFFFFFFFL);
          final int t2 = (int)(_timestamp & 0xFFFFFFFFL);
          Util.setBytesFromInt(result, 0, 4, t1);
          Util.setBytesFromInt(result, 4, 4, t2);
          Util.setBytesFromInt(result, 8, 4, _epochNumber);
          Util.setBytesFromInt(result,12, 4, _sequenceNumber);
  
          if (tc.isEntryEnabled()) Tr.exit(tc, "toBytes", Util.toHexString(result));
          return result;
      }
docs: Build a native TxPrimaryKey suitable for recreating with the mainline
  constructor.
  
  <pre>
  struct search_key_t {
  double        timestamp;
  unsigned long epochNumber;
  unsigned long sequenceNumber;
  };
  </pre>