class_docstr: An in-progress episode.
  
  Compared to EpisodeBatch, this datatype does less checking, only
  contains one episodes, and uses lists instead of numpy arrays to make
  stepping faster.
  
  Args:
      env (Environment): The environment the trajectory is being collected
          in.
      initial_observation (np.ndarray): The first observation. If None, the
          environment will be reset to generate this observation.
      episode_info (dict[str, np.ndarray]): Info for this episode.
  
  Raises:
      ValueError: if either initial_observation and episode_info is passed in
          but not the other. Either both or neither should be passed in.
docstr: np.ndarray: The last observation in the epside.
docstr_tok: ["np.ndarray",":","The","last","observation","in","the","epside","."]
code: def last_obs(self):
      """np.ndarray: The last observation in the epside."""
      return self.observations[-1]
  
imports: import collections
  import numpy
  from garage import EpisodeBatch, StepType
label_desc: Use image node_id 4 for calling the InProgressEpisode obj's underlying member method code with example usage: obj.last_obs() and returns: self