code: def _blend(img1, img2, alpha):
      """
      Weighted sum of two images
  
      Arguments
      ---------
      img1 : torch tensor
      img2 : torch tensor
      alpha : float between 0 and 1
          how much weight to put on img1 and 1-alpha weight
          to put on img2
      """
      return img1.mul(alpha).add(1 - alpha, img2)
  
imports: import random
  import torch
  from torchvision.transforms.functional import to_tensor
  import numpy
  from ..utils import th_random_choice
label_desc: Use image node_id 1 for calling a global function with example usage: _blend(img1, img2, alpha) and returns: img1