@Override
    public void serialize(SystemStreamPartition systemStreamPartition, JsonGenerator jsonGenerator, SerializerProvider provider) throws IOException,
                                                                                                                                        JsonProcessingException {
      Map<String, Object> systemStreamPartitionMap = new HashMap<String, Object>();
      systemStreamPartitionMap.put("system", systemStreamPartition.getSystem());
      systemStreamPartitionMap.put("stream", systemStreamPartition.getStream());
      systemStreamPartitionMap.put("partition", systemStreamPartition.getPartition());
      jsonGenerator.writeObject(systemStreamPartitionMap);
    }
Builds {@link ObjectNode} which matches the {@link JobModel} built in setup.
samza-core/src/test/java/org/apache/samza/serializers/model/TestSamzaObjectMapper.java