TYP: fix a couple errors flagged by pyright

Author: neutrinoceros

src/cmasher/_handlercolorpolycollection.py

@@ -1,24 +1,32 @@
+import sys
+
 import numpy as np
 from matplotlib.legend_handler import HandlerBase
 
+if sys.version_info >= (3, 12):
+    from typing import override
+else:
+    from typing_extensions import override
+
 
 # Define legend handler class for artists that use colormaps
 class _HandlerColorPolyCollection(HandlerBase):
     # Override create_artists to create an AxesImage resembling a colormap
+    @override
     def create_artists(
-        self, legend, artist, xdescent, ydescent, width, height, fontsize, trans
+        self, legend, orig_handle, xdescent, ydescent, width, height, fontsize, trans
     ):
         from matplotlib.image import AxesImage
 
         # Obtain the Axes object of this legend
         ax = legend.axes
 
         # Obtain the colormap of the artist
-        cmap = artist.cmap
+        cmap = orig_handle.cmap
 
         # Create an AxesImage to contain the colormap with proper dimensions
         image = AxesImage(
-            ax, cmap=cmap, transform=trans, extent=[xdescent, width, ydescent, height]
+            ax, cmap=cmap, transform=trans, extent=(xdescent, width, ydescent, height)
         )
 
         # Set the data of the image