Iterate dirs instead of using st_size

- stat-size is filesystem-specific, therefore it was not sufficient to
check for empty folders on all systems in feed_forward.py

share/example/feed_forward.py

@@ -46,8 +46,8 @@ class AllowEmptyClassImageFolder(ImageFolder):
     '''
     def find_classes(self, directory):
         with os.scandir(directory) as scanit:
-            class_info = sorted((entry.name, entry.stat().st_size) for entry in scanit if entry.is_dir())
-        class_to_idx = {class_name: index for index, (class_name, st_size) in enumerate(class_info) if st_size}
+            class_info = sorted((entry.name, len(list(os.scandir(entry.path)))) for entry in scanit if entry.is_dir())
+        class_to_idx = {class_name: index for index, (class_name, n_members) in enumerate(class_info) if n_members}
         if not class_to_idx:
             raise FileNotFoundError(f'No non-empty classes found in \'{directory}\'.')
         return list(class_to_idx), class_to_idx