@Override
    public Set<ContainerModel> group(Set<TaskModel> taskModels, List<String> containerIds) {
      // if task 0, then add to this map
      Map<TaskName, TaskModel> tasksForContainer0 = new HashMap<>();
      // all tasks that aren't task 0 go into this map
      Map<TaskName, TaskModel> tasksForContainer1 = new HashMap<>();
      taskModels.forEach(taskModel -> {
        if (taskName(0).equals(taskModel.getTaskName())) {
          tasksForContainer0.put(taskName(0), taskModel);
        } else {
          tasksForContainer1.put(taskModel.getTaskName(), taskModel);
        }
      });
      return ImmutableSet.of(new ContainerModel("0", tasksForContainer0), new ContainerModel("1", tasksForContainer1));
    }
Groups all SSPs into two tasks. The first task gets all of the SSPs with a partition id of 0. The second task gets
all other SSPs. This is used for testing a custom {@link SystemStreamPartitionGrouper}.
samza-core/src/test/java/org/apache/samza/coordinator/TestJobModelCalculator.java