Blocks a handler of an instance so it will not be called during any
signal emissions unless it is unblocked again. Thus "blocking" a
signal handler means to temporarily deactive it, a signal handler
has to be unblocked exactly the same amount of times it has been
blocked before to become active again.
The handler_id has to be a valid signal handler id, connected to a
signal of instance.
Blocks a handler of an instance so it will not be called during any signal emissions unless it is unblocked again. Thus "blocking" a signal handler means to temporarily deactive it, a signal handler has to be unblocked exactly the same amount of times it has been blocked before to become active again. The handler_id has to be a valid signal handler id, connected to a signal of instance.