code: def process_pil_image(image, quality=guetzli.DEFAULT_JPEG_QUALITY):
      
      image_rgb = _to_pil_rgb_image(image)
      image_rgb_bytes = image_rgb.tobytes()
      return guetzli.process_rgb_bytes(
              image_rgb_bytes,
              *image.size,
              quality=quality
              )
docs: Generates an optimized JPEG from a PIL image. If the image has an alpha
      channel (transparency), it will be overlaid on a black background.
  
      :param image: the PIL image
      :param quality: the output JPEG quality (default 95)
  
      :returns: Optimized JPEG bytes
      :rtype: bytes
  
      :raises ImportError: PIL / Pillow cannot be imported.
  
      .. code:: python
  
          import pyguetzli
          from PIL import Image
  
          image = Image.open("./test/image.jpg")
          optimized_jpeg = pyguetzli.process_pil_image(image)