Pytorch的permute函数，将tensor的维度换位

举例：

>>> x = torch.randn(2, 3, 5) 
>>> x.size() 
torch.Size([2, 3, 5]) 
>>> x.permute(2, 0, 1).size() 
torch.Size([5, 2, 3])

https://zhuanlan.zhihu.com/p/76583143