如何在pytorch中返回中间渐变(对于非叶子节点)？

import torch

# 定义模型
class MyModel(torch.nn.Module):
    def __init__(self):
        super(MyModel, self).__init__()
        self.fc1 = torch.nn.Linear(10, 5)
        self.fc2 = torch.nn.Linear(5, 1)

    def forward(self, x):
        x = self.fc1(x)
        x = torch.relu(x)
        x = self.fc2(x)
        return x

# 创建模型实例
model = MyModel()

# 输入数据
input_data = torch.randn(1, 10)

# 前向传播
output = model(input_data)

# 选择需要返回中间渐变的非叶子节点
intermediate_output = model.fc1(input_data)
intermediate_output.retain_grad()

# 反向传播
output.backward()

# 获取中间渐变的梯度值
gradient = intermediate_output.grad