docs: def convert(self, blob, size=500):
          """Size is the maximum horizontal size."""
          file_list = []
          with make_temp_file(blob) as in_fn, make_temp_file() as out_fn:
              try:
                  subprocess.check_call(["pdftoppm", "-jpeg", in_fn, out_fn])
                  file_list = sorted(glob.glob(f"{out_fn}-*.jpg"))
  
                  converted_images = []
                  for fn in file_list:
                      converted = resize(open(fn, "rb").read(), size, size)
                      converted_images.append(converted)
  
                  return converted_images
              except Exception as e:
                  raise ConversionError("pdftoppm failed") from e
              finally:
                  for fn in file_list:
                      try:
                          os.remove(fn)
                      except OSError:
                          pass