SerializableSchema should check if its values can be serialized, so that it doesn't break when used in a union with a base type or schema that isn't a SerializableSchema

src/c3nav/mapdata/schemas/model_base.py

@@ -41,7 +41,7 @@ class SerializableSchema(Schema):
     @classmethod
     def _run_root_validator(cls, values: Any, handler: ModelWrapValidatorHandler[Schema], info: ValidationInfo) -> Any:
         """ overwriting this, we need to call serialize to get the correct data """
-        if not isinstance(values, dict):
+        if hasattr(values, 'serialize') and callable(values.serialize):
             values = values.serialize()
         return handler(values)