async do() {
        if (this.operations.length === 0) {
            return Promise.resolve();
        }
        this.parallelExecute();
        return new Promise((resolve, reject) => {
            this.emitter.on("finish", resolve);
            this.emitter.on("error", (error) => {
                this.state = BatchStates.Error;
                reject(error);
            });
        });
    }
Start execute operations in the queue.