code: def test_unflatten_dict(self):
      expected_xs = {"foo": 1, "bar": {"a": 2}}
      xs = traverse_util.unflatten_dict(
          {
              ("foo",): 1,
              ("bar", "a"): 2,
          }
      )
      self.assertEqual(xs, expected_xs)
      xs = traverse_util.unflatten_dict(
          {
              "foo": 1,
              "bar/a": 2,
          },
          sep="/",
      )
      self.assertEqual(xs, expected_xs)
  
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 16 for calling the TraversalTest obj's underlying member method code with example usage: obj.test_unflatten_dict() without return types