forward() takes 2 positional arguments but 3 were given

问题描述：

在forward中明明正确数量的参数，却报错：forward() takes 2 positional arguments but 3 were given；

问题分析：

使用nn.Sequential()定义的网络，只接受单输入

例如：

self.backbone=nn.Sequential(nn.lstm(input_size=20, hidden_size=40, num_layers=2),

                                nn.linear(in_features=40, out_features=2))

def forward(self, input):

    h0 = torch.randn(hidden_layers, batch_size, hidden)

    c0 = torch.randn(hidden_layers, batch_size, hidden)
     output, _ = self.backbone(input)  **(对）**

     output, _ = self.backbone(input, (h0, c0)   （**错误，因为nn.Sequential()定义的网络，只接受单输入**）