code: def test_flatten_flax_to_haiku_toplevel(self):
      variables = {"params": {"w": 0}}
      hk_params = utils.flatten_flax_to_haiku(variables["params"])
      self.assertEqual(hk_params, {"~": {"w": 0}})
  
imports: from absl.testing import absltest
  from absl.testing import parameterized
  from haiku._src.flax import utils
label_desc: Use image node_id 2 for calling the UtilsTest obj's underlying member method code with example usage: obj.test_flatten_flax_to_haiku_toplevel() without return types