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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 set_event_handler(self, event, handler):
 """Add an Async to be run on event."""

        # QUESTION: Should we raise an exception if `event` is not in some
        # known event-type list?

        self._prepare_persistence_engine()

        callbacks = self._options.get('callbacks', {})
        callbacks[event] = handler
        self._options['callbacks'] = callbacks