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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 stop_app(self, callback_function_param=False):
 """ Stops the current running app on the Chromecast. """

        self.logger.info("Receiver:Stopping current app '%s'", self.app_id)
        return self.send_message(
            {MESSAGE_TYPE: 'STOP'},
            inc_session_id=True, callback_function=callback_function_param)