docs: def _gen_shuffles(self):
          '''
          Used internally to build a list for mapping between a random number and 
          a song index.
          '''
          # The current metasong index 
          si = 0
          # The shuffle mapper list
          self.shuffles = []
          # Go through all our songs...
          for song in self.loop:
              # And add them to the list as many times as they say to.
              for i in range(song[1]):
                  self.shuffles.append(si)
              si += 1