实例化 class 报错： NotImplementedError

这是我定义的模型

class CNN(nn.Module):
    def __init__(self):
        super(CNNcpl, self).__init__()
        self.conv1 = nn.Conv1d(20, 64, 5)
        self.pool1 = nn.AvgPool1d(4, 4)                
        self.conv2 = nn.Conv1d(64, 128, 5)
        self.pool2 = nn.AvgPool1d(4, 4)           
        self.conv3 = nn.Conv1d(128, 256, 5)
        self.pool3 = nn.AvgPool1d(4, 4)                 
        self.fc1 = nn.Linear(256*29, 64)
        self.fc2 = nn.Linear(64, 2)

    def forword(self, x):
        x = self.pool1(F.relu(self.conv1(x)))
        x = self.pool2(F.relu(self.conv2(x)))
        x = self.pool3(F.relu(self.conv3(x)))         
        x = x.reshape(256*29)
        x = F.relu(self.fc1(x))
        x = F.softmax(self.fc2(x), dim = 1 )
        return x

当我运行下面的代码时

cnn = CNN()
cnn(x)
# x 是一个 20*2000 的 tensor

报错

~/anaconda3/lib/python3.7/site-packages/torch/nn/modules/module.py in _call_impl(self, *input, **kwargs)
   1100         if not (self._backward_hooks or self._forward_hooks or self._forward_pre_hooks or _global_backward_hooks
   1101                 or _global_forward_hooks or _global_forward_pre_hooks):
-> 1102             return forward_call(*input, **kwargs)
   1103         # Do not call functions when jit is used
   1104         full_backward_hooks, non_full_backward_hooks = [], []

~/anaconda3/lib/python3.7/site-packages/torch/nn/modules/module.py in _forward_unimplemented(self, *input)
    199         registered hooks while the latter silently ignores them.
    200     """
--> 201     raise NotImplementedError
    202
    203

NotImplementedError:

这个类定义的有问题吗？我刚刚接触深度学习和 Python 不久，请各位大佬指教。