code: def testChooseFromDatasetsNested(self):
      ds1 = dataset_ops.Dataset.range(10).window(2)
      ds2 = dataset_ops.Dataset.range(10, 20).window(2)
      choice_dataset = dataset_ops.Dataset.range(2).repeat(5)
      ds = dataset_ops.Dataset.choose_from_datasets(
          [ds1, ds2], choice_dataset
      )
      ds = ds.flat_map(lambda x: x)
      expected = []
      for i in range(5):
          for j in range(2):
              expected.extend([10 * j + 2 * i, 10 * j + 2 * i + 1])
      self.assertDatasetProduces(ds, expected)
  
imports: from absl.testing import parameterized
  import numpy
  from tensorflow.python.data.kernel_tests import checkpoint_test_base
  from tensorflow.python.data.kernel_tests import test_base
  from tensorflow.python.data.ops import dataset_ops
  from tensorflow.python.data.ops import options
  from tensorflow.python.framework import combinations
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import errors
  from tensorflow.python.ops import stateless_random_ops
  from tensorflow.python.platform import test
label_desc: Use image node_id 5 for calling the ChooseFromDatasetsTest obj's underlying member method code with example usage: obj.testChooseFromDatasetsNested() without return types