code: def test_to_mutable_dict(self):
      before = FlatMap({"a": {"b": 1, "c": 2}})
      after = data_structures.to_mutable_dict(before)
      self.assertEqual(before, after)
      self.assertEqual(type(after), dict)
      self.assertEqual(type(after["a"]), dict)
  
imports: import collections
  import copy
  import pickle
  import threading
  from absl.testing import absltest
  from absl.testing import parameterized
  import cloudpickle
  import dill
  from haiku._src import data_structures
  import jax
  import tree
label_desc: Use image node_id 5 for calling the DataStructuresTest obj's underlying member method code with example usage: obj.test_to_mutable_dict() without return types