class Net(nn.Cell):
    """前向网络模型"""

    def __init__(self):
        super(Net,self).__init__()
        self.sin = ops.Sin()

    def construct(self,x):
        out = self.sin(x)
        return out

x_train = ms.Tensor(np.array([3.1415926]),dtype=ms.float32)

net = Net()
firstgrad = ms.grad(net)
secondgrad = ms.grad(firstgrad)
thirdgrad = ms.grad(secondgrad)

output = secondgrad(x_train)
output1 = thirdgrad(x_train)

#打印结果
result = np.around(output,asnumpy(),decimals=2)
print(result)
print(output1)

RuntimeError:Parameter[0] has no default param