@Override
  public Map<TaskName, LocationId> getTaskLocality() {
    return taskLocality;
  }
Implementation of {@link GrouperMetadata} that holds the necessary historical metadata of
the samza job. This is used by the {@link TaskNameGrouper} to generate optimal task assignments.
samza-core/src/main/java/org/apache/samza/container/grouper/task/GrouperMetadataImpl.java