code: def global_success_rate(self) -> float:
      return self._global_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 4 for calling the ZoneSuccessRate obj's underlying member method code with example usage: obj.global_success_rate() and returns: self