code: def brightness(var, image):
      """
      Perform color brightness on the given image.
      Args:
          var (float): variance.
          image (array): image to perform color brightness.
      Returns:
          (array): image that performed color brightness.
      """
      img_bright = np.zeros(image.shape).astype(image.dtype)
      alpha = 1.0 + np.random.uniform(-var, var)
      return blend(image, img_bright, alpha)
  
imports: import math
  import numpy
  import cv2
label_desc: Use image node_id 26 for calling a global function with example usage: brightness(var, image) and returns: blend