Fix syntax and dependency error for cifar

[yenchenlin]

1. pip install torchvision==0.4 results in the error:

ERROR: Could not find a version that satisfies the requirement torchvision==0.4 (from versions: 0.1.6, 0.1.7, 0.1.8, 0.1.9, 0.2.0, 0.2.1, 0.2.2, 0.2.2.post2, 0.2.2.post3, 0.8.2, 0.9.0, 0.9.1, 0.10.0, 0.10.1, 0.11.0, 0.11.1, 0.11.2, 0.11.3, 0.12.0, 0.13.0, 0.13.1, 0.14.0, 0.14.1)
ERROR: No matching distribution found for torchvision==0.4

2. From PyTorch 1.13 one should use next(iter(loader)) instead of iter(loader).next().