code: def test_order_instances(self):
      scheduler = RoundRobinScheduler(batch_size=4)
      epoch_instances = {
          "a": [1] * 5,
          "b": [2] * 3,
      }
      batches = scheduler.batch_instances(epoch_instances)
      assert list(batches) == [[1, 2, 1, 2], [1, 2, 1, 1]]
  
imports: from allennlp.data.data_loaders.multitask_scheduler import RoundRobinScheduler, HomogeneousRoundRobinScheduler
label_desc: Use image node_id 1 for calling the RoundRobinSchedulerTest obj's underlying member method code with example usage: obj.test_order_instances() without return types