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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def notify(self, n=1):
 """Raise the condition and wake up fibers waiting on it. The optional *n* parameter specifies how many fibers will be notified. By default, one fiber is notified. """

        if not is_locked(self._lock):
            raise RuntimeError('lock is not locked')
        notified = [0]  # Work around lack of "nonlocal" in py27
        def walker(switcher, predicate):
            if not switcher.active:
                return False  # not not keep switcher that timed out
            if predicate and not predicate():
                return True
            if n >= 0 and notified[0] >= n:
                return True
            switcher.switch()
            notified[0] += 1
            return False  # only notify once
        walk_callbacks(self, walker)