code: def get_tokens(file: Optional[str] = None) -> Tokens:
      global default_tokens
  
      if file is None:
          if default_tokens is None:
              default_tokens = Tokens.default_tokens()
          return default_tokens
      if file not in tokens:
          tokens[file] = Tokens.from_file(file)
      return tokens[file]
  
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 3 for calling a global function with example usage: get_tokens(file) and returns: tokens, default_tokens