code: def unregister_all(self, category: Optional[str] = None):
      remaining = set()
      for cat, key in self._registered:
          if category and category == cat:
              self.unregister(cat, key)
          else:
              remaining.add((cat, key))
      self._registered = remaining
  
imports: import atexit
  import logging
  from functools import partial
  from types import FunctionType
  from typing import Callable, Optional, Type, Union
  import ray
  import ray.cloudpickle
  from ray.experimental.internal_kv import _internal_kv_get, _internal_kv_initialized, _internal_kv_put, _internal_kv_del
  from ray.tune.error import TuneError
  from ray.util.annotations import DeveloperAPI
label_desc: Use image node_id 6 for calling the _Registry obj's underlying member method code with example usage: obj.unregister_all(category) without return types