code: def test_reconstruct_trajectories_toy_example(self):
      particles = tf.convert_to_tensor(
          [
              [1, 2, 3],
              [
                  4,
                  5,
                  6,
              ],
              [7, 8, 9],
          ]
      )
      # 1  --  4  -- 7
      # 2  \/  5  .- 8
      # 3  /\  6 /-- 9
      parent_indices = tf.convert_to_tensor(
          [[0, 1, 2], [0, 2, 1], [0, 2, 2]]
      )
  
      trajectories = self.evaluate(
          particle_filter.reconstruct_trajectories(
              particles, parent_indices
          )
      )
      self.assertAllEqual(
          np.array([[1, 2, 2], [4, 6, 6], [7, 8, 9]]), trajectories
      )
  
imports: import functools
  import numpy
  import tensorflow.compat.v2
  from tensorflow_probability.python.bijectors import shift
  from tensorflow_probability.python.distributions import bernoulli
  from tensorflow_probability.python.distributions import deterministic
  from tensorflow_probability.python.distributions import joint_distribution_auto_batched
  from tensorflow_probability.python.distributions import joint_distribution_named
  from tensorflow_probability.python.distributions import linear_gaussian_ssm
  from tensorflow_probability.python.distributions import mvn_diag
  from tensorflow_probability.python.distributions import mvn_tril
  from tensorflow_probability.python.distributions import normal
  from tensorflow_probability.python.distributions import poisson
  from tensorflow_probability.python.distributions import sample
  from tensorflow_probability.python.distributions import transformed_distribution
  from tensorflow_probability.python.distributions import uniform
  from tensorflow_probability.python.experimental.mcmc import particle_filter
  from tensorflow_probability.python.internal import prefer_static
  from tensorflow_probability.python.internal import test_util
  from tensorflow_probability.python.math import gradient
label_desc: Use image node_id 4 for calling the _ParticleFilterTest obj's underlying member method code with example usage: obj.test_reconstruct_trajectories_toy_example() without return types