why do I get this error, I pass in cifar10 images, [3, 32, 32] in size to this model
def conv_block(in_channels, out_channels, k):
    # set_trace()
    return nn.Sequential(
        nn.Conv2d(in_channels, out_channels, k, padding=0),
        nn.BatchNorm2d(out_channels),
        nn.ReLU(),
        nn.MaxPool2d(2)
    )

from IPython.core.debugger import set_trace

class Top(nn.Module):
  def __init__(self):
    super().__init__()
    self.encoder = conv_block(3, 16, 3)
    self.lin = nn.Linear(20, 10)
    self.childone = Second()
    self.childtwo = Second()
  def forward(self, x):
    # set_trace()
    a = self.childone(self.encoder(x))
    b = self.childtwo(self.encoder(x))
    # print('top', a.shape, b.shape)
    out = torch.cat((a, b), dim=-1)
    return self.lin(out) 

class Second(nn.Module):
  def __init__(self):
    super().__init__()
    self.encoder = conv_block(16, 32, 3)
    self.lin = nn.Linear(20, 10)
    self.childone = Middle()
    self.childtwo = Middle()

  def forward(self, x):
    a = self.childone(self.encoder(x))
    b = self.childtwo(self.encoder(x))
    # print('middle', a.shape, b.shape)
    out = torch.cat((a, b), dim=-1)
    return self.lin(out)

class Middle(nn.Module):
  def __init__(self):
    super().__init__()
    self.encoder = conv_block(32, 64, 1)
    self.lin = nn.Linear(20, 10)
    self.childone = Bottom()
    self.childtwo = Bottom()

  def forward(self, x):
    a = self.childone(self.encoder(x))
    b = self.childtwo(self.encoder(x))
    # print('middle', a.shape, b.shape)
    out = torch.cat((a, b), dim=-1)
    return self.lin(out)

class Bottom(nn.Module):
  def __init__(self):
    super().__init__()
    self.encoder = conv_block(64, 128, 1)
    self.lin_one = nn.Linear(128, 10)
  def forward(self, x):
    
    # print('bottom', x.shape)
    out = self.encoder(x)
    return (self.lin_one(out.view(out.size(0), -1)))

model = Top()
# inp = [None, train_dataset[0][0]]
model.to('cuda')