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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 stream_url(self):
 """Build url for stream."""

        rtsp_url = RTSP_URL.format(
            host=self.config.host, video=self.video_query,
            audio=self.audio_query, event=self.event_query)
        _LOGGER.debug(rtsp_url)
        return rtsp_url