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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 get_media_uri(self, item_id):
 """Get a streaming URI for an item. Note: You should not need to use this directly. It is used by the Sonos players (not the controllers) to obtain the uri of the media stream. If you want to have a player play a media item, you should add add it to the queue using its id and let the player work out where to get the stream from (see `On Demand Playback <http://musicpartners.sonos.com/node/421>`_ and `Programmed Radio <http://musicpartners.sonos.com/node/422>`_) Args: item_id (str):
 The item for which the URI is required Returns: str: The item's streaming URI. """

        response = self.soap_client.call(
            'getMediaURI',
            [('id', item_id)])
        return response.get('getMediaURIResult', None)