code: def test_calculate_mean_and_var_from_sample_paths_zero_sigma(
      self, dtype
  ):
      atol = 1e-12
      num_samples = 100
      sample_paths = np.ones((num_samples, 2, 1), dtype=dtype)
      (mean, var, std_err_mean, std_err_var) = self.evaluate(
          gmb_utils.calculate_mean_and_variance_from_sample_paths(
              sample_paths, num_samples, dtype
          )
      )
  
      expected_mean = np.ones((2), dtype=dtype) * np.log(1.0)
      zeros = np.zeros((2), dtype=dtype)
      self.assertArrayNear(
          mean, expected_mean, atol, msg="comparing means"
      )
      self.assertArrayNear(var, zeros, atol, msg="comparing vars")
      self.assertArrayNear(
          std_err_mean, zeros, atol, msg="comparing std error of means"
      )
      self.assertArrayNear(
          std_err_var, zeros, atol, msg="comparing std error of vars"
      )
  
file_path: tf-quant-finance/tf_quant_finance/models/geometric_brownian_motion/geometric_brownian_motion_test_utils_test.py
imports: from absl.testing import parameterized
  import numpy
  import tensorflow.compat.v2
  from tensorflow.python.framework import test_util
  from tf_quant_finance.models.geometric_brownian_motion import geometric_brownian_motion_test_utils
label_desc: Use image node_id 3 for calling the GeometricBrownianMotionTestUtilsTest obj's underlying member method code with example usage: obj.test_calculate_mean_and_var_from_sample_paths_zero_sigma(dtype) without return types