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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 durationSeconds(self):
 """ Returns the runtime duration of the video stream as a floating point number of seconds. Returns 0.0 if not a video stream. """

        f=0.0
        if self.isVideo() or self.isAudio():
            if self.__dict__['duration']:
                try:
                    f=float(self.__dict__['duration'])
                except Exception as e:
                    print "None numeric duration"
        return f