public static String serialize(KafkaStateCheckpointMarker marker) {
    try {
      return MAPPER.writeValueAsString(marker);
    } catch (JsonProcessingException e) {
      throw new SamzaException(String.format("Error serializing KafkaCheckpointMarker %s", marker), e);
    }
  }
It is used for serde'ing {@link KafkaStateCheckpointMarker}s, in conjunction with {@link #deserialize(String)}.
@return the String representation of this {@link KafkaStateCheckpointMarker}
samza-core/src/main/java/org/apache/samza/checkpoint/kafka/KafkaStateCheckpointMarker.java