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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 form_uri(item_id, service, is_track):
 """Form and return a music service item uri Args: item_id (str):
 The item id service (MusicService):
 The music service that the item originates from is_track (bool):
 Whether the item_id is from a track or not Returns: str: The music service item uri """

    if is_track:
        uri = service.sonos_uri_from_id(item_id)
    else:
        uri = 'x-rincon-cpcontainer:' + item_id
    return uri