Convert some custom sort comparison functions to equivalent key functions.
diff --git a/Lib/idlelib/configDialog.py b/Lib/idlelib/configDialog.py
index e7a0690..d0e4066 100644
--- a/Lib/idlelib/configDialog.py
+++ b/Lib/idlelib/configDialog.py
@@ -980,16 +980,11 @@
         self.SetThemeType()
         ##load theme element option menu
         themeNames = list(self.themeElements.keys())
-        themeNames.sort(self.__ThemeNameIndexCompare)
+        themeNames.sort(key=lambda x: self.themeElements[x][1])
         self.optMenuHighlightTarget.SetMenu(themeNames,themeNames[0])
         self.PaintThemeSample()
         self.SetHighlightTarget()
 
-    def __ThemeNameIndexCompare(self,a,b):
-        if self.themeElements[a][1]<self.themeElements[b][1]: return -1
-        elif self.themeElements[a][1]==self.themeElements[b][1]: return 0
-        else: return 1
-
     def LoadKeyCfg(self):
         ##current keys type radiobutton
         self.keysAreBuiltin.set(idleConf.GetOption('main','Keys','default',