code: def test_jpf():
      with Image.open("Tests/images/balloon.jpf") as im:
          assert im.format == "JPEG2000"
          assert im.get_format_mimetype() == "image/jpx"
  
imports: import os
  import re
  from io import BytesIO
  import pytest
  from PIL import Image, ImageFile, Jpeg2KImagePlugin, UnidentifiedImageError, features
  from .helper import assert_image_equal, assert_image_similar, assert_image_similar_tofile, skip_unless_feature
label_desc: Use image node_id 3 for calling a global function with example usage: test_jpf() without return types