code: def test_traversal_id(self):
      x = 1
      traversal = traverse_util.t_identity
      self.assertEqual(list(traversal.iterate(x)), [1])
      y = traversal.update(lambda x: x + x, x)
      self.assertEqual(y, 2)
  
imports: import collections
  import jax
  import jax.numpy
  import numpy
  import optax
  from absl.testing import absltest
  import flax
  from flax import traverse_util
  from flax.core import freeze
label_desc: Use image node_id 1 for calling the TraversalTest obj's underlying member method code with example usage: obj.test_traversal_id() without return types