How to use the home-assistant-js-websocket.subscribeServices function in home-assistant-js-websocket

broadcastConnectionStatus("connected");

      conn.addEventListener("ready", () => this.hassReconnected());
      conn.addEventListener("disconnected", () => this.hassDisconnected());
      // If we reconnect after losing connection and auth is no longer valid.
      conn.addEventListener("reconnect-error", (_conn, err) => {
        if (err === ERR_INVALID_AUTH) {
          broadcastConnectionStatus("auth-invalid");
          location.reload();
        }
      });

      subscribeEntities(conn, (states) => this._updateHass({ states }));
      subscribeConfig(conn, (config) => this._updateHass({ config }));
      subscribeServices(conn, (services) => this._updateHass({ services }));
      subscribePanels(conn, (panels) => this._updateHass({ panels }));
    }

window.hassConnection.then(({ conn }) => {
  const noop = () => {
    // do nothing
  };
  subscribeEntities(conn, noop);
  subscribeConfig(conn, noop);
  subscribeServices(conn, noop);
  subscribePanels(conn, noop);
  subscribeThemes(conn, noop);
  subscribeUser(conn, noop);

  if (location.pathname === "/" || location.pathname.startsWith("/lovelace/")) {
    (window as WindowWithLovelaceProm).llConfProm = fetchConfig(conn, false);
  }
});

// Client events
        this.client.addEventListener('ready', this.onClientOpen.bind(this));
        this.client.addEventListener(
            'disconnected',
            this.onClientClose.bind(this)
        );
        this.client.addEventListener(
            'reconnect-error',
            this.onClientError.bind(this)
        );

        // Home Assistant Events
        homeassistant.subscribeEntities(this.client, ent =>
            this.onClientStates(ent)
        );
        homeassistant.subscribeServices(this.client, ent =>
            this.onClientServices(ent)
        );
        homeassistant.subscribeConfig(this.client, config =>
            this.onClientConfigUpdate(config)
        );

        return true;
    }