code: def test_flatten(self):
      frozen = freeze({"c": 1, "b": {"a": 2}})
      flat_leaves, tdef = jax.tree_util.tree_flatten(frozen)
      self.assertEqual(flat_leaves, [2, 1])
      self.assertEqual(
          jax.tree_util.tree_unflatten(tdef, flat_leaves),
          frozen,
      )
      flat_path_leaves, tdef = jax.tree_util.tree_flatten_with_path(
          frozen
      )
      self.assertEqual(
          flat_path_leaves,
          [
              (
                  (
                      jax.tree_util.DictKey("b"),
                      jax.tree_util.DictKey("a"),
                  ),
                  2,
              ),
              ((jax.tree_util.DictKey("c"),), 1),
          ],
      )
      self.assertEqual(
          jax.tree_util.tree_unflatten(
              tdef, [l for _, l in flat_path_leaves]
          ),
          frozen,
      )
  
file_path: flax/tests/core/core_frozen_dict_test.py
imports: import jax
  from absl.testing import absltest, parameterized
  from flax.core import FrozenDict, copy, freeze, pop, pretty_repr, unfreeze
label_desc: Use image node_id 14 for calling the FrozenDictTest obj's underlying member method code with example usage: obj.test_flatten() without return types