Pytorch: 向 Conv2d 提供 3d 输入会给出错误消息

import torch
import torch.nn as nn
from torch.autograd import Variable

m = Variable(torch.randn(3, 10, 20))
nn.Conv2d(in_channels=3, out_channels=8, kernel_size=3)(m)

Traceback (most recent call last):
  File "too.py", line 6, in <module>
    nn.Conv2d(in_channels=3, out_channels=8, kernel_size=3)(m)
  File "/home/soumith/code/pytorch/torch/nn/modules/module.py", line 206, in __call__
    result = self.forward(*input, **kwargs)
  File "/home/soumith/code/pytorch/torch/nn/modules/conv.py", line 237, in forward
    self.padding, self.dilation, self.groups)
  File "/home/soumith/code/pytorch/torch/nn/functional.py", line 43, in conv2d
    return f(input, weight, bias)
RuntimeError: expected 3D tensor