例如：y = a2x + bx + c，分別對a，b，c求導

若當a=3，b=4，c=5，x=1時

import torch
from torch import autogradx = torch.tensor(1.)
a = torch.tensor(3.,requires_grad=True)
b = torch.tensor(4.,requires_grad=True)
c = torch.tensor(5.,requires_grad=True)y = a**2 * x + b * x + cprint("before:",a.grad,b.grad,c.grad)#before: None None None
grads = autograd.grad(y,[a,b,c])
print("after:",grads[0],grads[1],grads[2])#after: tensor(6.) tensor(1.) tensor(1.)