code: def save_rpm(self):
      save_path = os.path.join(logger.get_dir(), "rpm.npz")
      self.rpm.save(save_path)
  
imports: import os
  import parl
  import queue
  import six
  import threading
  import time
  import numpy
  from actor import Actor
  from opensim_model import OpenSimModel
  from opensim_agent import OpenSimAgent
  from parl.utils import logger, summary, get_gpu_count
  from replay_memory import ReplayMemory
  from parl.utils.window_stat import WindowStat
  from parl.remote.client import get_global_client
  from parl.utils import machine_info
label_desc: Use image node_id 8 for calling the Learner obj's underlying member method code with example usage: obj.save_rpm() without return types