Issue title: FileNotFoundError: [Errno 2] No such file or directory: './data/imagenet/train_map.txt'
 Issue body: Hi @ancientmooner @zdaxie , 

Thanks for your contribution, but why there need a txt file to load ImageNet?
 Comments: 
 Comment 0: Hello, did you managed to get that file?
 Comment 1: Hello, did you solve this question. 
I have the same question.
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