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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 deallocate(self, buf):
 """ Return buffers to the pool. If they are of the poolable size add them to the free list, otherwise just mark the memory as free. Arguments: buffer_ (io.BytesIO):
 The buffer to return """

        with self._lock:
            # BytesIO.truncate here makes the pool somewhat pointless
            # but we stick with the BufferPool API until migrating to
            # bytesarray / memoryview. The buffer we return must not
            # expose any prior data on read().
            buf.truncate(0)
            self._free.append(buf)
            if self._waiters:
                self._waiters[0].notify()