code: def get_variables(self, sigma, sigma_down):
      t, t_next = [to_neg_log_sigma(s) for s in (sigma, sigma_down)]
      h = t_next - t
      s = t + 0.5 * h
      return h, s, t, t_next
  
imports: from typing import Dict, Union
  import torch
  from omegaconf import ListConfig, OmegaConf
  from tqdm import tqdm
  from ...modules.diffusionmodules.sampling_utils import get_ancestral_step, linear_multistep_coeff, to_d, to_neg_log_sigma, to_sigma
  from ...util import append_dims, default, instantiate_from_config
label_desc: Use image node_id 1 for calling the DPMPP2SAncestralSampler obj's underlying member method code with example usage: obj.get_variables(sigma, sigma_down) and returns: h,  s,  t,  t_next