private static SystemStreamPartitionGrouper getSystemStreamPartitionGrouper(Config config) {
    String factoryString = new JobConfig(config).getSystemStreamPartitionGrouperFactory();
    SystemStreamPartitionGrouperFactory factory =
        ReflectionUtil.getObj(factoryString, SystemStreamPartitionGrouperFactory.class);
    return factory.getSystemStreamPartitionGrouper(config);
  }
Finds the {@see SystemStreamPartitionGrouperFactory} from the {@param config}. Instantiates the
{@see SystemStreamPartitionGrouper} object through the factory.
@param config the configuration of the samza job.
@return the instantiated {@see SystemStreamPartitionGrouper}.
samza-core/src/main/java/org/apache/samza/coordinator/JobModelCalculator.java