Overrides the class closure (i.
e. the default handler) for the given signal for emissions on instances of instance_type. instance_type must be
derived from the type to which the signal belongs.
See chain_from_overridden and chain_from_overridden_handler for how to chain up to the parent class closure from inside the overridden one.
| signal_id |
the signal id |
| instance_type |
the instance type on which to override the class closure for the signal. |
| class_closure |
the closure. |