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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 get_dependency(self, worker_ctx):
 """ Inject a dispatch method onto the service instance """

        extra_headers = self.get_message_headers(worker_ctx)

        def dispatch(event_type, event_data):
            self.publisher.publish(
                event_data,
                exchange=self.exchange,
                routing_key=event_type,
                extra_headers=extra_headers
            )

        return dispatch