docstr: Checks that the dataset is not prematurely materialized.
docstr_tok: ["Checks","that","the","dataset","is","not","prematurely","materialized","."]
code: def testDeferred(self):
      """Checks that the dataset is not prematurely materialized."""
      self.validate_deferred_materialization(
          vectorized_stochastic_volatility.VectorizedStochasticVolatility,
          centered_returns=_test_dataset(),
      )
  
imports: import functools
  from absl import logging
  from absl.testing import parameterized
  import numpy
  import tensorflow.compat.v2
  import tensorflow_probability
  from tensorflow_probability.python.internal import test_util
  from inference_gym.internal import test_util
  from inference_gym.targets import vectorized_stochastic_volatility
  from tensorflow.python.util import nest
label_desc: Use image node_id 2 for calling the VectorizedStochasticVolatilityTest obj's underlying member method code with example usage: obj.testDeferred() without return types