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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 close(self):
 """ Close terminates a session with NATS Streaming. """


        # Remove the core NATS Streaming subscriptions.
        await self._close()

        req = protocol.CloseRequest()
        req.clientID = self._client_id
        msg = await self._nc.request(
            self._close_req_subject,
            req.SerializeToString(),
            self._connect_timeout,
            )
        resp = protocol.CloseResponse()
        resp.ParseFromString(msg.data)

        if resp.error != "":
            raise StanError(resp.error)