248 lines
8.1 KiB
Python
248 lines
8.1 KiB
Python
# Copyright 2022-present MongoDB, Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from __future__ import annotations
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import asyncio
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import collections
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import os
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import threading
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import time
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import weakref
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from typing import Any, Callable, Optional, TypeVar
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_HAS_REGISTER_AT_FORK = hasattr(os, "register_at_fork")
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# References to instances of _create_lock
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_forkable_locks: weakref.WeakSet[threading.Lock] = weakref.WeakSet()
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_T = TypeVar("_T")
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def _create_lock() -> threading.Lock:
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"""Represents a lock that is tracked upon instantiation using a WeakSet and
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reset by pymongo upon forking.
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"""
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lock = threading.Lock()
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if _HAS_REGISTER_AT_FORK:
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_forkable_locks.add(lock)
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return lock
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def _release_locks() -> None:
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# Completed the fork, reset all the locks in the child.
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for lock in _forkable_locks:
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if lock.locked():
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lock.release()
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# Needed only for synchro.py compat.
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def _Lock(lock: threading.Lock) -> threading.Lock:
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return lock
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class _ALock:
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__slots__ = ("_lock",)
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def __init__(self, lock: threading.Lock) -> None:
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self._lock = lock
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def acquire(self, blocking: bool = True, timeout: float = -1) -> bool:
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return self._lock.acquire(blocking=blocking, timeout=timeout)
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async def a_acquire(self, blocking: bool = True, timeout: float = -1) -> bool:
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if timeout > 0:
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tstart = time.monotonic()
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while True:
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acquired = self._lock.acquire(blocking=False)
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if acquired:
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return True
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if timeout > 0 and (time.monotonic() - tstart) > timeout:
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return False
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if not blocking:
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return False
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await asyncio.sleep(0)
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def release(self) -> None:
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self._lock.release()
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async def __aenter__(self) -> _ALock:
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await self.a_acquire()
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return self
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def __enter__(self) -> _ALock:
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self._lock.acquire()
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return self
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def __exit__(self, exc_type: Any, exc: Any, tb: Any) -> None:
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self.release()
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async def __aexit__(self, exc_type: Any, exc: Any, tb: Any) -> None:
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self.release()
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def _safe_set_result(fut: asyncio.Future) -> None:
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# Ensure the future hasn't been cancelled before calling set_result.
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if not fut.done():
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fut.set_result(False)
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class _ACondition:
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__slots__ = ("_condition", "_waiters")
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def __init__(self, condition: threading.Condition) -> None:
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self._condition = condition
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self._waiters: collections.deque = collections.deque()
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async def acquire(self, blocking: bool = True, timeout: float = -1) -> bool:
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if timeout > 0:
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tstart = time.monotonic()
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while True:
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acquired = self._condition.acquire(blocking=False)
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if acquired:
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return True
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if timeout > 0 and (time.monotonic() - tstart) > timeout:
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return False
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if not blocking:
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return False
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await asyncio.sleep(0)
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async def wait(self, timeout: Optional[float] = None) -> bool:
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"""Wait until notified.
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If the calling task has not acquired the lock when this
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method is called, a RuntimeError is raised.
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This method releases the underlying lock, and then blocks
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until it is awakened by a notify() or notify_all() call for
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the same condition variable in another task. Once
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awakened, it re-acquires the lock and returns True.
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This method may return spuriously,
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which is why the caller should always
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re-check the state and be prepared to wait() again.
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"""
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loop = asyncio.get_running_loop()
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fut = loop.create_future()
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self._waiters.append((loop, fut))
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self.release()
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try:
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try:
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try:
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await asyncio.wait_for(fut, timeout)
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return True
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except asyncio.TimeoutError:
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return False # Return false on timeout for sync pool compat.
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finally:
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# Must re-acquire lock even if wait is cancelled.
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# We only catch CancelledError here, since we don't want any
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# other (fatal) errors with the future to cause us to spin.
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err = None
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while True:
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try:
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await self.acquire()
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break
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except asyncio.exceptions.CancelledError as e:
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err = e
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self._waiters.remove((loop, fut))
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if err is not None:
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try:
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raise err # Re-raise most recent exception instance.
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finally:
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err = None # Break reference cycles.
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except BaseException:
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# Any error raised out of here _may_ have occurred after this Task
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# believed to have been successfully notified.
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# Make sure to notify another Task instead. This may result
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# in a "spurious wakeup", which is allowed as part of the
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# Condition Variable protocol.
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self.notify(1)
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raise
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async def wait_for(self, predicate: Callable[[], _T]) -> _T:
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"""Wait until a predicate becomes true.
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The predicate should be a callable whose result will be
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interpreted as a boolean value. The method will repeatedly
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wait() until it evaluates to true. The final predicate value is
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the return value.
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"""
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result = predicate()
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while not result:
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await self.wait()
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result = predicate()
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return result
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def notify(self, n: int = 1) -> None:
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"""By default, wake up one coroutine waiting on this condition, if any.
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If the calling coroutine has not acquired the lock when this method
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is called, a RuntimeError is raised.
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This method wakes up at most n of the coroutines waiting for the
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condition variable; it is a no-op if no coroutines are waiting.
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Note: an awakened coroutine does not actually return from its
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wait() call until it can reacquire the lock. Since notify() does
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not release the lock, its caller should.
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"""
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idx = 0
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to_remove = []
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for loop, fut in self._waiters:
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if idx >= n:
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break
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if fut.done():
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continue
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try:
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loop.call_soon_threadsafe(_safe_set_result, fut)
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except RuntimeError:
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# Loop was closed, ignore.
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to_remove.append((loop, fut))
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continue
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idx += 1
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for waiter in to_remove:
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self._waiters.remove(waiter)
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def notify_all(self) -> None:
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"""Wake up all threads waiting on this condition. This method acts
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like notify(), but wakes up all waiting threads instead of one. If the
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calling thread has not acquired the lock when this method is called,
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a RuntimeError is raised.
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"""
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self.notify(len(self._waiters))
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def locked(self) -> bool:
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"""Only needed for tests in test_locks."""
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return self._condition._lock.locked() # type: ignore[attr-defined]
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def release(self) -> None:
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self._condition.release()
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async def __aenter__(self) -> _ACondition:
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await self.acquire()
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return self
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def __enter__(self) -> _ACondition:
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self._condition.acquire()
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return self
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async def __aexit__(self, exc_type: Any, exc: Any, tb: Any) -> None:
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self.release()
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def __exit__(self, exc_type: Any, exc: Any, tb: Any) -> None:
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self.release()
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