如何使用PyTorch只对矩阵的上三角元素进行softmax？

import torch
import torch.nn.functional as F

matrix = torch.tensor([[1.0, 2.0, 3.0],
                       [4.0, 5.0, 6.0],
                       [7.0, 8.0, 9.0]])

upper_triangular = torch.triu(matrix)

softmaxed_upper_triangular = F.softmax(upper_triangular, dim=1)

print(softmaxed_upper_triangular)