Added type hints

src/PIL/Image.py

@@ -2643,7 +2643,7 @@ def transform(
         resample=Resampling.NEAREST,
         fill=1,
         fillcolor=None,
-    ):
+    ) -> Image:
         """
         Transforms this image.  This method creates a new image with the
         given size, and the same mode as the original, and copies data

src/PIL/ImageTransform.py

@@ -14,17 +14,21 @@
 #
 from __future__ import annotations
 
+from typing import Sequence
+
 from . import Image
 
 
 class Transform(Image.ImageTransformHandler):
-    def __init__(self, data):
+    method: int
+
+    def __init__(self, data: Sequence[int]) -> None:
         self.data = data
 
-    def getdata(self):
+    def getdata(self) -> tuple[int, Sequence[int]]:
         return self.method, self.data
 
-    def transform(self, size, image, **options):
+    def transform(self, size: tuple[int, int], image: Image.Image, **options: dict[str, str | int | tuple[int, ...] | list[int]]) -> Image.Image:
         # can be overridden
         method, data = self.getdata()
         return image.transform(size, method, data, **options)