.. note::
- The :meth:`acquire` method of :class:`BoundedSemaphore`, :class:`Lock`,
- :class:`RLock` and :class:`Semaphore` has a timeout parameter not supported
- by the equivalents in :mod:`threading`. The signature is
- ``acquire(block=True, timeout=None)`` with keyword parameters being
- acceptable. If *block* is ``True`` and *timeout* is not ``None`` then it
- specifies a timeout in seconds. If *block* is ``False`` then *timeout* is
- ignored.
-
On Mac OS X, ``sem_timedwait`` is unsupported, so calling ``acquire()`` with
a timeout will emulate that function's behavior using a sleeping loop.