I get the following error

```
IndexError: Dimension out of range (expected to be in range of [-1, 0], but got 1)
```

from this line: ` x = torch.cat([a, b], 1)`

in the snippet code below:

```
class Critic(nn.Module):
def __init__(self, input_size, hidden_size, output_size):
super(Critic, self).__init__()
self.linear1 = nn.Linear(input_size, hidden_size)
self.linear2 = nn.Linear(hidden_size, hidden_size)
self.linear3 = nn.Linear(hidden_size, output_size)
def forward(self, a, b):
x = torch.cat([a, b], 1)
x = F.relu(self.linear1(x))
x = F.relu(self.linear2(x))
x = self.linear3(x)
return x
```

Any help on this appreciated.