docstr: Checks approximate samples from the model against the ground truth.
docstr_tok: ["Checks","approximate","samples","from","the","model","against","the","ground","truth","."]
code: def testSP500SmallHMC(self):
      """Checks approximate samples from the model against the ground truth."""
      self.skipTest("Broken by omnistaging b/168705919")
      model = (
          vectorized_stochastic_volatility.VectorizedStochasticVolatilitySP500Small()
      )
  
      self.validate_ground_truth_using_hmc(
          model,
          num_chains=4,
          num_steps=500,
          num_leapfrog_steps=15,
          step_size=1.0,
          use_xla=BACKEND
          == "backend_jax",  # TF XLA is very slow on this problem
      )
  
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 7 for calling the VectorizedStochasticVolatilityTest obj's underlying member method code with example usage: obj.testSP500SmallHMC() without return types