n type of the scheduler function, one of epsilon (predicting the noise of the diffusion
process), sample (directly predicting the noisy sample) or v_prediction` (see section 2.4
https://imagen.research.google/video/paper.pdf)



Scheduler created by @crowsonkb in k_diffusion, see:
https://github.com/crowsonkb/k-diffusion/blob/5b3af030dd83e0297272d861c19477735d0317ec/k_diffusion/sampling.py#L188
Scheduler inspired by DPM-Solver-2 and Algorthim 2