logits is a (batch, classes) tensor of raw multi-class scores. Return
the predicted class index for each sample in the batch (softmax then argmax along
the class dimension).
Input
tensor([[2.0000, 1.0000, 0.1000],
[0.1000, 3.0000, 0.2000],
[1.0000, 1.0000, 5.0000]])
Output
tensor([0, 1, 2])