<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 async def start_client(self, sock: anyio.abc.SocketStream, addr, path: str, headers: Optional[List] = None, subprotocols: Optional[List[str]] = None):
 """Start a client WS connection on this socket. Returns: the AcceptConnection message. """

        self._sock = sock
        self._connection = WSConnection(ConnectionType.CLIENT)
        if headers is None:
            headers = []
        if subprotocols is None:
            subprotocols = []
        data = self._connection.send(
            Request(
                host=addr[0],
                target=path,
                extra_headers=headers,
                subprotocols=subprotocols))
        await self._sock.send_all(data)

        assert self._scope is None
        self._scope = True
        try:
            event = await self._next_event()
            if not isinstance(event, AcceptConnection):
                raise ConnectionError("Failed to establish a connection",
                                      event)
            return event
        finally:
            self._scope = None