code: def test_stack_frames_axis(self):
      env = StackFrames(
          DummyDiscrete2DEnv(random=False),
          n_frames=self.n_frames,
          axis=0,
      )
      env.reset()
      obs, _, _, _ = env.step(1)
      assert obs.shape[0] == self.n_frames
  
      env = StackFrames(
          DummyDiscrete2DEnv(random=False),
          n_frames=self.n_frames,
          axis=2,
      )
      env.reset()
      obs, _, _, _ = env.step(1)
      assert obs.shape[2] == self.n_frames
  
file_path: garage/tests/garage/envs/wrappers/test_stack_frames_env.py
imports: import gym.spaces
  import numpy
  import pytest
  from garage.envs.wrappers import StackFrames
  from tests.fixtures.envs.dummy import DummyDiscrete2DEnv
label_desc: Use image node_id 8 for calling the TestStackFrames obj's underlying member method code with example usage: obj.test_stack_frames_axis() without return types