Update conf.py

Author: RobPasMue

doc/source/conf.py

@@ -86,7 +86,7 @@
     # Remove sphinx configuration comments from code blocks
     "remove_config_comments": True,
     # Sort gallery example by file name instead of number of lines (default)
-    "within_subsection_order": FileNameSortKey,
+    "within_subsection_order": "FileNameSortKey"
     # directory where function granular galleries are stored
     "backreferences_dir": None,
     # Modules for which function level galleries are created.  In