The device to which the timesteps should be moved to. If None, the timesteps are not moved.    Sets the discrete timesteps used for the diffusion chain (to be run before inference).  step  < source > ( model_output: FloatTensor sigma_hat: float sigma_prev: float sample_hat: FloatTensor return_dict: bool = True  ) → ~schedulers.scheduling_karras_ve.KarrasVESchedulerOutput or tuple  Parameters   model_output (torch.FloatTensor) —