def acquire(self):
        assert self.tokens >= 0, "Internal inconsistency??  tokens should never be negative"
        d = Deferred(canceller=self._cancelAcquire)
        if not self.tokens:
            self.waiting.append(d)
        else:
            self.tokens = self.tokens - 1
            d.callback(self)
        return d
Returns a list of all the files under the given directory. Directories are
dataset/ETHPy150Open twisted/twisted/twisted/internet/defer.py/DeferredSemaphore.acquire--crossover with--dataset/ETHPy150Open brownhead/superzippy/superzippy/tests/file_utilities.py/get_files