code: def env_key(self) -> str:
      return "CFLEARN_ENV"
  
file_path: carefree-learn/cflearn/parameters.py
imports: import os
  from typing import Any
  from typing import Dict
  from cftool.misc import OPTBase
label_desc: Use image node_id 1 for calling the OPTClass obj's underlying member method code with example usage: obj.env_key() and returns: str