Define a function named posterize. This function expects an image and a tuple of RGB values as arguments. The function modifies the image like the blackAndWhite function developed in Chapter 7 and shown below, but it uses passed in RGB values instead of black

def posterize(image, rgb):
  for pixel in image.getPixels():
    pixel.red = rgb[0]
    pixel.green = rgb[1]
    pixel.blue = rgb[2]
  return image