code: def save_state_to_checkpoint(
      self, checkpoint_dir: str, checkpoint_prefix: int
  ):
      dict_to_save = {
          "_mean": self._mean,
          "_std": self._std,
          "_count": self._count,
          "_sum": self._sum,
          "_sum_squares": self._sum_squares,
      }
  
      with open(
          os.path.join(
              checkpoint_dir,
              str(checkpoint_prefix)
              + "."
              + self.checkpoint_file_extension,
          ),
          "wb",
      ) as f:
          pickle.dump(dict_to_save, f, pickle.HIGHEST_PROTOCOL)
  
imports: import os
  from abc import ABC, abstractmethod
  import threading
  import pickle
  import redis
  import numpy
  from rl_coach.utils import get_latest_checkpoint
label_desc: Use image node_id 11 for calling the NumpySharedRunningStats obj's underlying member method code with example usage: obj.save_state_to_checkpoint(checkpoint_dir, checkpoint_prefix) without return types