code: def _get_zone_counter(self, zone: str):
      zone_counter = self._zone_counters.get(zone)
      if not zone_counter:
          zone_counter = WindowFractionCounter(10)
          self._zone_counters[zone] = zone_counter
      return zone_counter
  
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 2 for calling the ZoneSuccessRate obj's underlying member method code with example usage: obj._get_zone_counter(zone) and returns: zone_counter