class_docstr: Checkpoints data from Reverb replay buffer.
class_docstr_tok: ["Checkpoints","data","from","Reverb","replay","buffer","."]
code: def _save_fn(self) -> None:
      checkpoint_path = self._reverb_client.checkpoint()
      logging.info("Checkpointing Reverb data to %s", checkpoint_path)
  
imports: import os
  from typing import Mapping, Optional, Sequence, Text, Tuple, Union
  from absl import logging
  import tensorflow.compat.v2
  from tf_agents.agents import tf_agent
  from tf_agents.metrics import py_metric
  from tf_agents.policies import async_policy_saver
  from tf_agents.policies import greedy_policy
  from tf_agents.policies import policy_saver
  from tf_agents.policies import tf_policy
  from tf_agents.train import interval_trigger
  from tf_agents.train import learner
  from tf_agents.train import step_per_second_tracker
  from tf_agents.typing import types
label_desc: Use image node_id 2 for calling the ReverbCheckpointTrigger obj's underlying member method code with example usage: obj._save_fn() without return types