code: def test_save_and_restore(self, mock_learner):
      learner = frozen_learner.FrozenLearner(mock_learner)
  
      mock_learner.save.return_value = "state1"
  
      state = learner.save()
      self.assertEqual(state, "state1")
  
      learner.restore("state2")
      # State of the wrapped learner should be restored.
      mock_learner.restore.assert_called_once_with("state2")
  
file_path: acme/acme/utils/frozen_learner_test.py
imports: from unittest import mock
  import acme
  from acme.utils import frozen_learner
  from absl.testing import absltest
label_desc: Use image node_id 3 for calling the FrozenLearnerTest obj's underlying member method code with example usage: obj.test_save_and_restore(mock_learner) without return types