code: def contrast(var, image):
      """
      Perform color contrast on the given image.
      Args:
          var (float): variance.
          image (array): image to perform color contrast.
      Returns:
          (array): image that performed color contrast.
      """
      img_gray = grayscale(image)
      img_gray.fill(np.mean(img_gray[0]))
      alpha = 1.0 + np.random.uniform(-var, var)
      return blend(image, img_gray, alpha)
  
imports: import math
  import numpy
  import cv2
label_desc: Use image node_id 27 for calling a global function with example usage: contrast(var, image) and returns: blend