code: def namespace_token_with_expiration(
      self, ns: str
  ) -> Optional[Tuple[str, Optional[float]]]:
      if token := self._tokens.get(ns):
          return token, None
      return None
  
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 8 for calling the Tokens obj's underlying member method code with example usage: obj.namespace_token_with_expiration(ns) and returns: None, token,  None