Make AbstractSlide.set_cache() non-abstract

It was added in 1.2.0, so any older third-party subclass may not implement
the method.  In addition, most subclasses will want this method to do
nothing, matching ImageSlide's implementation.  Make the default
implementation do nothing and remove the method override from ImageSlide.

Signed-off-by: Benjamin Gilbert <[email protected]>

Author: bgilbert

openslide/__init__.py

@@ -161,12 +161,13 @@ def read_region(
         size:     (width, height) tuple giving the region size."""
         raise NotImplementedError
 
-    @abstractmethod
-    def set_cache(self, cache: OpenSlideCache) -> None:
+    def set_cache(self, cache: OpenSlideCache) -> None:  # noqa: B027
         """Use the specified cache to store recently decoded slide tiles.
 
+        This class does not support caching, so this method does nothing.
+
         cache: an OpenSlideCache object."""
-        raise NotImplementedError
+        pass
 
     def get_thumbnail(self, size: tuple[int, int]) -> Image.Image:
         """Return a PIL.Image containing an RGB thumbnail of the image.
@@ -486,14 +487,6 @@ def read_region(
             tile.info['icc_profile'] = self._profile
         return tile
 
-    def set_cache(self, cache: OpenSlideCache) -> None:
-        """Use the specified cache to store recently decoded slide tiles.
-
-        ImageSlide does not support caching, so this method does nothing.
-
-        cache: an OpenSlideCache object."""
-        pass
-
 
 def open_slide(filename: lowlevel.Filename) -> OpenSlide | ImageSlide:
     """Open a whole-slide or regular image.