code: def form_uri(item_content, item_class):
          
          extension = None
          if 'mime_type' in item_content:
              extension = MIME_TYPE_TO_EXTENSION[item_content['mime_type']]
          out = URIS.get(item_class)
          if out:
              out = out.format(extension=extension, **item_content)
          return out
docs: Form the URI for a music service element.
  
          :param item_content: The content dict of the item
          :type item_content: dict
          :param item_class: The class of the item
          :type item_class: Sub-class of
              :py:class:`soco.data_structures.MusicServiceItem`