code: def __getitem__(self, item):
      pass
  
file_path: alibi/alibi/explainers/backends/cfrl_base.py
imports: import numpy
  from typing import Callable, Any, Optional
  from abc import ABC, abstractmethod
label_desc: Use image node_id 3 for calling the CounterfactualRLDataset obj's underlying member method code with example usage: obj.__getitem__(item) without return types