code: def default_tokens() -> "Tokens":
      tokens_file = Tokens.get_tokens_file()
      if os.path.isfile(tokens_file):
          with open(tokens_file, "r", encoding="utf-8") as f:
              log.info(f"tokens loaded from {tokens_file}")
              return Tokens(json.load(f))
      log.info(f"tokens file not found: {tokens_file}")
      return Tokens({})
  
imports: from typing import Optional, Dict, Tuple
  import base64
  import collections.abc
  import os
  import json
  import logging
  from hailtop.config import get_deploy_config
  from hailtop.utils import first_extant_file
label_desc: Use image node_id 2 for calling the Tokens obj's underlying member method code with example usage: obj.default_tokens() and returns: Tokens, Tokens