code: def testSingleBucket(self):
      def _map_fn(v):
          return (
              v,
              array_ops.fill([v], v),
              array_ops.fill([3], string_ops.as_string(v)),
          )
  
      input_dataset = dataset_ops.Dataset.from_tensor_slices(
          math_ops.range(32)
      ).map(_map_fn)
  
      bucketed_dataset = input_dataset.group_by_window(
          key_func=lambda x, y, z: 0,
          reduce_func=lambda k, bucket: self._dynamicPad(k, bucket, 32),
          window_size=32,
      )
      get_next = self.getNext(bucketed_dataset)
  
      which_bucket, bucketed_values = self.evaluate(get_next())
  
      self.assertEqual(0, which_bucket)
  
      expected_scalar_int = np.arange(32, dtype=np.int64)
      expected_unk_int64 = np.zeros((32, 31)).astype(np.int64)
      for i in range(32):
          expected_unk_int64[i, :i] = i
      expected_vec3_str = np.vstack(3 * [np.arange(32).astype(bytes)]).T
  
      self.assertAllEqual(expected_scalar_int, bucketed_values[0])
      self.assertAllEqual(expected_unk_int64, bucketed_values[1])
      self.assertAllEqual(expected_vec3_str, bucketed_values[2])
  
imports: from absl.testing import parameterized
  import numpy
  from tensorflow.core.lib.core import error_codes_pb2
  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.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.framework import ops
  from tensorflow.python.framework import tensor_shape
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import string_ops
  from tensorflow.python.platform import test
label_desc: Use image node_id 2 for calling the GroupByWindowTest obj's underlying member method code with example usage: obj.testSingleBucket() and returns: v,  array_ops,  array_ops