code: def test_prob(self):
      sample = self.distrib.sample()
      sample_prob = self.distrib.prob(sample)
      for b in range(self.batch_size):
          cov = np.identity(self.ndim, dtype=np.float32) * self.var[b]
          desired_pdf = scipy.stats.multivariate_normal(
              self.mean[b], cov
          ).pdf(sample.array[b])
          np.testing.assert_allclose(
              sample_prob.array[b], desired_pdf, rtol=1e-5
          )
  
imports: import unittest
  import chainer
  from chainer import testing
  from chainer.testing import condition
  import numpy
  import scipy.stats
  from chainerrl import distribution
label_desc: Use image node_id 4 for calling the TestGaussianDistribution obj's underlying member method code with example usage: obj.test_prob() without return types