How to use the rsp-client.RSPClient function in rsp-client

export async function initClient(serverInfo: ServerInfo): Promise {
    const client = new RSPClient('localhost', serverInfo.port);
    await client.connect();

    client.getIncomingHandler().onPromptString(event => {
        return new Promise((resolve, reject) => {
            vscode.window.showInputBox({ prompt: event.prompt, password: true })
                .then(value => {
                    if (value && value.trim().length) {
                        resolve(value);
                    } else {
                        reject(new Error('Cancelled by user'));
                    }
                });
        });
    });

    client.getOutgoingHandler().registerClientCapabilities(