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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 sounds(self):
 """Return a dictionary of sounds recognized by Pushover and that can be used in a notification message. """

        if not Pushover._SOUNDS:
            request = Request("get", SOUND_URL, {"token": self.token})
            Pushover._SOUNDS = request.answer["sounds"]
        return Pushover._SOUNDS