Fix errors detected by Ruff (#3918)

### What problem does this PR solve?

Fix errors detected by Ruff

### Type of change

- [x] Refactoring

api/db/db_models.py

@@ -130,7 +130,7 @@ def is_continuous_field(cls: typing.Type) -> bool:
     for p in cls.__bases__:
         if p in CONTINUOUS_FIELD_TYPE:
             return True
-        elif p != Field and p != object:
+        elif p is not Field and p is not object:
             if is_continuous_field(p):
                 return True
     else: