docstr: Tests that the default value of mean is 0.
docstr_tok: ["Tests","that","the","default","value","of","mean","is","0","."]
code: def test_mean_default(self):
      """Tests that the default value of mean is 0."""
      covar = np.array([[1.0, 0.1], [0.1, 1.0]])
      sample = self.evaluate(
          tff_rnd.mv_normal_sample(
              [40000], covariance_matrix=covar, seed=1234
          )
      )
      with self.subTest("Shape"):
          np.testing.assert_array_equal(sample.shape, [40000, 2])
      with self.subTest("Mean"):
          self.assertArrayNear(
              np.mean(sample, axis=0), [0.0, 0.0], 1e-2
          )
      with self.subTest("Covariance"):
          self.assertArrayNear(
              np.cov(sample, rowvar=False).reshape([-1]),
              covar.reshape([-1]),
              2e-2,
          )
  
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 2 for calling the RandomTest obj's underlying member method code with example usage: obj.test_mean_default() without return types