docstr: maintain recent obs for training
docstr_tok: ["maintain","recent","obs","for","training"]
code: def recent_obs(self):
      """maintain recent obs for training"""
      lst = list(self._context)
      obs = [np.zeros(self.obs_shape, dtype="uint8")] * (
          self._context.maxlen - len(lst)
      )
      obs.extend([k.obs for k in lst])
      return obs
  
file_path: PARL/benchmark/fluid/DQN_variant/replay_memory.py
imports: import numpy
  import copy
  from collections import deque, namedtuple
label_desc: Use image node_id 3 for calling the ReplayMemory obj's underlying member method code with example usage: obj.recent_obs() and returns: obs