<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def concat(self, arrs:Collection[Tensor])->Tensor:
        "Concatenate the `arrs` along the batch dimension."
        return [torch.cat([l[si] for l in arrs], dim=1) for si in range_of(arrs[0])]