code: def contrast_list(var, images):
      """
      Perform color contrast on the given list of images.
      Args:
          var (float): variance.
          images (list): list of images to perform color contrast.
      Returns:
          (array): image that performed color contrast.
      """
      alpha = 1.0 + np.random.uniform(-var, var)
  
      out_images = []
      for image in images:
          img_gray = grayscale(image)
          img_gray.fill(np.mean(img_gray[0]))
          out_images.append(blend(image, img_gray, alpha))
      return out_images
  
imports: import math
  import numpy
  import cv2
label_desc: Use image node_id 30 for calling a global function with example usage: contrast_list(var, images) and returns: out_images