You could write a custom module and pass add it to nn.Sequential.
Something like this might work:
class Narrow(nn.Module):
    def __init__(self, dim, start, length):
        super(Narrow, self).__init__()
        self.dim = dim
        self.start = start
        self.length = length
    
    def forward(self, x):
        x = torch.narrow(x, self.dim, self.start, self.length)
        return x