code: def test_order_instances(self):
      scheduler = HomogeneousRoundRobinScheduler({"a": 2, "b": 3})
      epoch_instances = {
          "a": [1] * 9,
          "b": [2] * 9,
      }
      flattened = scheduler.batch_instances(epoch_instances)
      assert list(flattened) == [
          [1, 1],
          [2, 2, 2],
          [1, 1],
          [2, 2, 2],
          [1, 1],
          [2, 2, 2],
          [1, 1],
          [1],
      ]
  
imports: from allennlp.data.data_loaders.multitask_scheduler import RoundRobinScheduler, HomogeneousRoundRobinScheduler
label_desc: Use image node_id 1 for calling the HomogeneousRoundRobinSchedulerTest obj's underlying member method code with example usage: obj.test_order_instances() without return types