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):
  img = image.copy()
  for row in range(img.getHeight()):
    for col in range(img.getWidth()):
      p = img.getPixel(col, row)
      if p.getRed() < rgb[0]:
        r = 0
      elif p.getRed() > rgb[0]:
        r = 255
      else:
        r = p.getRed()
      if p.getGreen() < rgb[1]:
        g = 0
      elif p.getGreen() > rgb[1]:
        g = 255
      else:
        g = p.getGreen()
      if p.getBlue() < rgb[2]:
        b = 0
      elif p.getBlue() > rgb[2]:
        b = 255
      else:
        b = p.getBlue()
      newPixel = image.Pixel(r, g, b)
      img.setPixel(col, row, newPixel)
  return img