How to use the snitun.multiplexer.message.CHANNEL_FLOW_CLOSE function in snitun

async def test_close_channel_msg():
    """Test close MultiplexerChannel."""
    output = asyncio.Queue()
    channel = MultiplexerChannel(output, IP_ADDR)
    assert isinstance(channel.uuid, UUID)

    message = channel.init_close()

    assert message.channel_id == channel.uuid
    assert message.flow_type == CHANNEL_FLOW_CLOSE
    assert message.data == b""

def init_close(self) -> MultiplexerMessage:
        """Init close message for transport."""
        _LOGGER.debug("Close channel %s", self._id)
        return MultiplexerMessage(self._id, CHANNEL_FLOW_CLOSE)

if not self._new_connections:
                _LOGGER.warning("Request new Channel is not allow")
                return

            ip_address = bytes_to_ip_address(message.extra[1:5])
            channel = MultiplexerChannel(
                self._queue,
                ip_address,
                channel_id=message.channel_id,
                throttling=self._throttling,
            )
            self._channels[channel.uuid] = channel
            self._loop.create_task(self._new_connections(self, channel))

        # Close
        elif message.flow_type == CHANNEL_FLOW_CLOSE:
            # check if message exists
            if message.channel_id not in self._channels:
                _LOGGER.debug("Receive close from unknown channel")
                return
            channel = self._channels.pop(message.channel_id)
            channel.close()

        # Ping
        elif message.flow_type == CHANNEL_FLOW_PING:
            if message.extra.startswith(b"pong"):
                _LOGGER.debug("Receive pong from peer / reset healthy")
                self._healthy.set()
            else:
                _LOGGER.debug("Receive ping from peer / send pong")
                self._write_message(
                    MultiplexerMessage(