code: def test_second_reset(self):
      original_env = FakeNonZeroObservationEnvironment()
      env = wrappers.FrameStackingWrapper(original_env, 2)
      action_spec = env.action_spec()
  
      env.reset()
      env.step(action_spec.generate_value())
      timestep = env.reset()
      self.assertTrue(np.all(timestep.observation[..., 0] == 0))
  
file_path: acme/acme/wrappers/frame_stacking_test.py
imports: from acme import wrappers
  from acme.testing import fakes
  import numpy
  import tree
  from absl.testing import absltest
label_desc: Use image node_id 3 for calling the FrameStackingTest obj's underlying member method code with example usage: obj.test_second_reset() without return types