docs: def filesizes(images):
      """Stat filesize of files.
  
      Args:
          images: stream of marv image files
  
      Returns:
          Stream of filesizes
      """
      # Pull each image and push its filesize
      while True:
          img = yield marv.pull(images)
          if img is None:
              break
          yield marv.push(img.size)