code: def ancestral_euler_step(self, x, denoised, sigma, sigma_down):
      d = to_d(x, sigma, denoised)
      dt = append_dims(sigma_down - sigma, x.ndim)
  
      return self.euler_step(x, d, dt)
  
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 2 for calling the AncestralSampler obj's underlying member method code with example usage: obj.ancestral_euler_step(x, denoised, sigma, sigma_down) and returns: self