docstr: Tests the expected total variance calculation.
docstr_tok: ["Tests","the","expected","total","variance","calculation","."]
code: def test_expected_total_variance_batch(self):
      """Tests the expected total variance calculation."""
      mean_reversion = 1.3
      theta = 0.2
      process = HestonModel(
          mean_reversion=mean_reversion,
          theta=theta,
          volvol=0.01,
          rho=-0.0,
          dtype=np.float64,
      )
      future_time = np.array([0.1, 1.0, 2.0])
      initial_var = np.array([0.1, 0.2, 0.3])
      expected_var = self.evaluate(
          process.expected_total_variance(future_time, initial_var)
      )
      ground_var = (initial_var - theta) * (
          1 - np.exp(-mean_reversion * future_time)
      ) / mean_reversion + theta * future_time
      np.testing.assert_allclose(expected_var, ground_var)
  
file_path: tf-quant-finance/tf_quant_finance/models/heston/heston_model_test.py
imports: from absl.testing import parameterized
  import numpy
  import tensorflow.compat.v2
  import tf_quant_finance
  from tensorflow.python.framework import test_util
label_desc: Use image node_id 5 for calling the HestonModelTest obj's underlying member method code with example usage: obj.test_expected_total_variance_batch() without return types