message: [tf.data] test zipped datasets with different processing modes
diff: @@ -442,7 +442,8 @@ class DataServiceOpsTest(data_service_test_base.TestBase,
  results = {}
  for _ in range(elements_to_read):
  val = next(it).numpy()
  - if val not in results: results[val] = 0
  + if val not in results:
  + results[val] = 0
  results[val] += 1
  for i in range(num_elements):
  self.assertGreater(results[i], elements_to_read / num_elements / 2)
  @@ -527,6 +528,21 @@ class DataServiceOpsTest(data_service_test_base.TestBase,
  data_service_ops.distribute(
  processing_mode="invalid", service="grpc://localhost:5000"))
  + @combinations.generate(test_base.eager_only_combinations())
  + def testZipMultipleProcessingModes(self):
  + cluster = self.create_cluster(num_workers=2)
  + num_elements = 100
  + ds1 = dataset_ops.Dataset.range(num_elements)
  + ds1 = self.make_distributed_dataset(
  + ds1, cluster, processing_mode="distributed_epoch")
  + ds2 = dataset_ops.Dataset.range(num_elements)
  + ds2 = self.make_distributed_dataset(
  + ds2, cluster, processing_mode="parallel_epochs")
  + ds = dataset_ops.Dataset.zip(ds1, ds2)
  + self.assertDatasetProduces(
  + ds, list(zip(range(num_elements), range(num_elements))),
  + assert_items_equal=True)
  +
  @combinations.generate(test_base.eager_only_combinations())
  def testFromDatasetId(self):
  cluster = self.create_cluster(num_workers=1)
  