Pytorch dataloader 设置 num_worker

https://www.codeleading.com/article/7316314042/
https://www.jianshu.com/p/4a1a92f0efd9

if __name__ == '__main__':应该加在最前端, 不然均会有问题 (在文件最开端写一句print('Hello World!'), 会多次输出)