def register(key, proc = nil, &block)
      Helper.register(obj: self, key: key, proc: proc, block: block)
    end
def register(key, proc = nil, &block)
      Helper.register(obj: self, key: key, proc: proc, block: block)
    end
Registers a new callback in the registry. This will add a new method
 matching +key+ to the registry that can be used both outside the
 registry and when registering other callbacks dependant of the
 current entry. Results from the callback will not be cached, meaning
 that the callback may return a different object every time.

 @param [String|Symbol] key
 @param [Proc|nil] proc
 @return [nil]