code: def testParallelVarianceOneAtATime(self):
      x = np.random.randn(5, 10)
      n, avg, m2, m2_c = 1, x[0], 0, 0
      for row in range(1, 5):
          (
              n,
              avg,
              m2,
              m2_c,
          ) = tensor_normalizer.parallel_variance_calculation(
              n_a=n,
              avg_a=avg,
              m2_a=m2,
              n_b=1,
              avg_b=x[row],
              m2_b=0,
              m2_b_c=m2_c,
          )
      var = m2 / n
      self.assertAllClose(avg, x.mean(axis=0))
      self.assertAllClose(var, x.var(axis=0))
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import functools
  from absl.testing import parameterized
  import numpy
  import tensorflow
  from tf_agents.specs import tensor_spec
  from tf_agents.utils import tensor_normalizer
label_desc: Use image node_id 1 for calling the ParallelVarianceTest obj's underlying member method code with example usage: obj.testParallelVarianceOneAtATime() without return types