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

async start() {
        const existing = await HomeAssistant.getStates(this.master.connection);

        for (let entity of existing)
            this._maybeAddEntity(entity.entity_id, entity.state, entity.attributes);

        this._unsubscribe = this.master.connection.subscribeEvents((event) => {
            const { entity_id, new_state } = event.data;
            if (new_state)
                this._maybeAddEntity(entity_id, new_state.state, new_state.attributes);
            else
                this._maybeDeleteEntity(entity_id);
        }, 'state_changed');
    }