code: def compute_psnr(a, b):
      """Compute Peak-Signal-to-Noise-Ratio across two numpy.ndarray objects"""
      max_b = np.abs(b).max()
      sumdeltasq = 0.0
  
      sumdeltasq = ((a - b) * (a - b)).sum()
  
      sumdeltasq /= b.size
      sumdeltasq = np.sqrt(sumdeltasq)
  
      eps = 1e-5
      eps2 = 1e-10
      psnr = 20 * np.log10((max_b + eps) / (sumdeltasq + eps2))
  
      return psnr
  
imports: import numpy
  import time
  import torch
label_desc: Use image node_id 2 for calling a global function with example usage: compute_psnr(a, b) and returns: psnr