code: def _force(self):
      if self._out is None:
          self._out = np.concatenate(self._frames, axis=-1)
          self._frames = None
      return self._out
  
file_path: garage/tests/fixtures/envs/dummy/dummy_discrete_pixel_env_baselines.py
imports: import gym
  import numpy
  from tests.fixtures.envs.dummy import DummyEnv
label_desc: Use image node_id 2 for calling the LazyFrames obj's underlying member method code with example usage: obj._force() and returns: self