code: def zone_success_rate(self, zone) -> float:
      zone_counter = self._get_zone_counter(zone)
      return zone_counter.fraction()
  
imports: import collections
  import logging
  import random
  from typing import Any, Dict, List, Set, Tuple
  from hailtop.aiocloud import aiogoogle
  from hailtop.utils import url_basename
  from ....driver.exceptions import RegionsNotSupportedError
  from ....driver.location import CloudLocationMonitor
  from ....utils import WindowFractionCounter
label_desc: Use image node_id 5 for calling the ZoneSuccessRate obj's underlying member method code with example usage: obj.zone_success_rate(zone) and returns: zone_counter