code: def test_image_grab():
      for test_file in test_files:
          with Image.open(test_file) as im:
              assert im.tell() == 0
              im0 = im.tobytes()
              im.seek(1)
              assert im.tell() == 1
              im1 = im.tobytes()
              im.seek(0)
              assert im.tell() == 0
              im02 = im.tobytes()
              assert im0 == im02
              assert im0 != im1
  
imports: from io import BytesIO
  import pytest
  from PIL import Image
  from .helper import assert_image_similar, is_pypy, skip_unless_feature
label_desc: Use image node_id 18 for calling a global function with example usage: test_image_grab() without return types