Should I register a backward hook on a module before or after adding it to a nn.sequential network?

1

For example should I be registering the hook before adding the module to the net:

net = nn.sequential 
test_module = TestLoss(number_value)
test_module.register_backward_hook(TestLoss.backward_hook)
net.add_module(str("test1"), test_module)

Or after:

net = nn.sequential 
test_module = TestLoss(number_value)
net.add_module(str("test1"), test_module)
test_module.register_backward_hook(TestLoss.backward_hook)