code: def test_nested_sequence(self):
      f_map = FlatMap({"foo": [1, 2], "bar": [{"a": 1}, 2]})
      leaves, _ = jax.tree_util.tree_flatten(f_map)
  
      self.assertEqual(leaves, [1, 2, 1, 2])
      self.assertEqual(f_map["foo"][0], 1)
  
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 26 for calling the FlatMappingTest obj's underlying member method code with example usage: obj.test_nested_sequence() without return types