Update _pil_constants.py (#6154)

* Update _pil_constants.py

* Update _pil_constants.py

* Fix flake8

* Fixed two related warnings in tests

* switch dir with hasattr
Co-authored-by: Vasilis Vryniotis <datumbox@users.noreply.github.com>

test/test_transforms.py

@@ -1522,10 +1522,10 @@ def test_ten_crop(should_vflip, single_dim):
     five_crop.__repr__()
 
     if should_vflip:
-        vflipped_img = img.transpose(Image.FLIP_TOP_BOTTOM)
+        vflipped_img = img.transpose(_pil_constants.FLIP_TOP_BOTTOM)
         expected_output += five_crop(vflipped_img)
     else:
-        hflipped_img = img.transpose(Image.FLIP_LEFT_RIGHT)
+        hflipped_img = img.transpose(_pil_constants.FLIP_LEFT_RIGHT)
         expected_output += five_crop(hflipped_img)
 
     assert len(results) == 10

torchvision/transforms/_pil_constants.py

-import PIL
 from PIL import Image
 
 # See https://pillow.readthedocs.io/en/stable/releasenotes/9.1.0.html#deprecations
 # TODO: Remove this file once PIL minimal version is >= 9.1
 
-if tuple(int(part) for part in PIL.__version__.split(".")) >= (9, 1):
+if hasattr(Image, "Resampling"):
     BICUBIC = Image.Resampling.BICUBIC
     BILINEAR = Image.Resampling.BILINEAR
     LINEAR = Image.Resampling.BILINEAR