code: def get_song_currency(self, cache=True):
          
          if not (cache and ('song_currency' in self.cache)):
              response = self.get_attribute('profile', bucket='song_currency')
              self.cache['song_currency'] = response['songs'][0]['song_currency']
          return self.cache['song_currency']
docs: Args:
              cache (bool): A boolean indicating whether or not the cached value should be used (if available). Defaults to True.
          
          Returns:
              A float representing a song's currency rank.
              
          Example:
              >>> s = song.Song('SOQKVPH12A58A7AF4D')
              >>> s.get_song_currency()
              0.639626025843539
              >>> s.song_currency
              0.639626025843539
              >>>