public void toDataPre_GEODE_1_15_0_0(DataOutput out,
      SerializationContext context) throws IOException {
    toDataPre_GEODE_1_14_0_0(out, context);
    boolean hasTransaction = transactionId != null;
    DataSerializer.writeBoolean(hasTransaction, out);
    if (hasTransaction) {
      DataSerializer.writeBoolean(isLastEventInTransaction, out);
      context.getSerializer().writeObject(transactionId, out);
    }
  }
If the value owned of this event is just bytes return that byte array; otherwise serialize the
value object and return the serialized bytes. Use {@link #getValueIsObject()} to determine if
the result is raw or serialized bytes.
geode-core/src/main/java/org/apache/geode/internal/cache/wan/GatewaySenderEventImpl.java