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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 realtime_stream(self, channel=1, typeno=0, path_file=None):
 """ If the stream is redirect to a file, use mplayer tool to visualize the video record camera.realtime_stream(path_file="/home/user/Desktop/myvideo) $ mplayer /home/user/Desktop/myvideo """

        ret = self.command(
            'realmonitor.cgi?action=getStream&channel={0}&subtype={1}'.format(
                channel, typeno)
        )

        if path_file:
            with open(path_file, 'wb') as out_file:
                shutil.copyfileobj(ret.raw, out_file)

        return ret.raw