fix commas

history_tracking/mixins.py

@@ -0,0 +1,23 @@
+# history_tracking/mixins.py
+
+
+class HistoricalChangeMixin:
+    @property
+    def diff_against_previous(self):
+        prev_record = self.prev_record
+        if not prev_record:
+            return {}
+
+        changes = {}
+        for field in self.__dict__:
+            if field not in [
+                "history_date",
+                "history_id",
+                "history_type",
+                "history_user_id",
+            ] and not field.startswith("_"):
+                old_value = getattr(prev_record, field)
+                new_value = getattr(self, field)
+                if old_value != new_value:
+                    changes[field] = {"old": old_value, "new": new_value}
+        return changes