Describe the current behavior / 问题描述 (Mandatory / 必填)

tensor hook，用外部变量获取梯度失败

Environment / 环境信息 (Mandatory / 必填)

• Hardware Environment(Ascend/GPU/CPU) / 硬件环境:
  /device ascend/GPU/CPU

• Software Environment / 软件环境 (Mandatory / 必填):
  -- MindSpore version (e.g., 1.7.0.Bxxx) :
  -- Python version (e.g., Python 3.7.5) :
  -- OS platform and distribution (e.g., Linux Ubuntu 16.04):
  -- GCC/Compiler version (if compiled from source):

• Excute Mode / 执行模式 (Mandatory / 必填)(PyNative/Graph):
  /mode pynative

Related testcase / 关联用例 (Mandatory / 必填)

from mindspore.nn import Cell
from mindspore import ops
from mindspore.common import Tensor
import numpy as np


class Net1(Cell):
    def __init__(self):
        super().__init__()
        self.n = 2

    def construct(self, x):
        return x * self.n


def test_hook_tensor_print():
    my_grad = None
    def print_fn(grad):
        my_grad = grad
        return grad

    net = Net1()
    x = np.random.rand(3,).astype(np.float32)
    x = Tensor(x)
    x.register_hook(print_fn)
    grad_net = ops.grad(net)
    grad = grad_net(x)
    print(my_grad)

Steps to reproduce the issue / 重现步骤 (Mandatory / 必填)

Describe the expected behavior / 预期结果 (Mandatory / 必填)

[2. 2. 2.]

Related log / screenshot / 日志 / 截图 (Mandatory / 必填)

None

Special notes for this issue/备注 (Optional / 选填)