code: def update(self, delta_seconds):
          
  
          for obj in tuple(self.current_tweens):
              for tween in tuple(self.current_tweens[obj]):
                  done = tween.update(delta_seconds)
                  if done:
                      self.current_tweens[obj].remove(tween)
                      if tween.on_complete: tween.on_complete(tween.target)
  
              if not self.current_tweens[obj]:
                  del self.current_tweens[obj]
  
          return self.current_tweens
docs: update tweeners. delta_seconds is time in seconds since last frame