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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def register_led_updates(self, callback, button):
 """Register a callback when a specific button LED changes."""

        button_callbacks = self._button_observer_callbacks.get(button)
        if not button_callbacks:
            self._button_observer_callbacks[button] = []
        _LOGGER.debug('New callback for button %d', button)
        self._button_observer_callbacks[button].append(callback)