Fix typing issues with SigLip2 (#37356)

* Fix issues

* Fix comment

---------

Co-authored-by: Pavel Iakubovskii <qubvel@gmail.com>

Author: EricWiener

src/transformers/image_processing_utils_fast.py

@@ -691,8 +691,12 @@ def preprocess(self, images: ImageInput, **kwargs: Unpack[DefaultFastImageProces
 
         # torch resize uses interpolation instead of resample
         resample = kwargs.pop("resample")
+
+        # Check if resample is an int before checking if it's an instance of PILImageResampling
+        # because if pillow < 9.1.0, resample is an int and PILImageResampling is a module.
+        # Checking PILImageResampling will fail with error `TypeError: isinstance() arg 2 must be a type or tuple of types`.
         kwargs["interpolation"] = (
-            pil_torch_interpolation_mapping[resample] if isinstance(resample, (PILImageResampling, int)) else resample
+            pil_torch_interpolation_mapping[resample] if isinstance(resample, (int, PILImageResampling)) else resample
         )
 
         # Pop kwargs that are not needed in _preprocess

src/transformers/models/siglip2/image_processing_siglip2.py

@@ -163,7 +163,7 @@ class Siglip2ImageProcessor(BaseImageProcessor):
     def __init__(
         self,
         do_resize: bool = True,
-        resample: PILImageResampling = PILImageResampling.BILINEAR,
+        resample: "PILImageResampling" = PILImageResampling.BILINEAR,
         do_rescale: bool = True,
         rescale_factor: float = 1 / 255,
         do_normalize: bool = True,
@@ -195,7 +195,7 @@ def preprocess(
         self,
         images: ImageInput,
         do_resize: Optional[bool] = None,
-        resample: Optional[PILImageResampling] = None,
+        resample: Optional["PILImageResampling"] = None,
         do_rescale: Optional[bool] = None,
         rescale_factor: Optional[float] = None,
         do_normalize: Optional[bool] = None,