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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:
 async def pop_transaction_async(self):
 """Decrement async transaction depth. """

        depth = self.transaction_depth_async()
        if depth > 0:
            depth -= 1
            self._task_data.set('depth', depth)
            if depth == 0:
                conn = self._task_data.get('conn')
                self._async_conn.release(conn)
        else:
            raise ValueError("Invalid async transaction depth value")