code: def append(self, exp):
      self.buffer.append(exp)
  
file_path: PARL/examples/tutorials/homework/lesson3/dqn_mountaincar/replay_memory.py
imports: import random
  import collections
  import numpy
label_desc: Use image node_id 2 for calling the ReplayMemory obj's underlying member method code with example usage: obj.append(exp) without return types