@Override
  public SamzaRelTableKeyConverter create(SystemStream systemStream, Config config) {
    return relConverters.computeIfAbsent(systemStream, ss -> new SampleRelTableKeyConverter());
  }
A sample {@link SamzaRelTableKeyConverterFactory} used in tests to create {@link SampleRelTableKeyConverter}.
samza-sql/src/test/java/org/apache/samza/sql/util/SampleRelTableKeyConverterFactory.java