docs: def set_music(self, plylst, force=False):
          '''
          Use to set the playlist to @plylst. If @force is False, the playlist 
          will not be set if it is @plylst already.
          '''
          plylst = plylst.lower()
          if plylst != self.cur_playlist or force:
              self.cur_playlist = plylst
              self.play_song(self.get_playlist().begin())