diff --git a/panther/app.py b/panther/app.py
index 82c523e..ba5452e 100644
--- a/panther/app.py
+++ b/panther/app.py
@@ -151,15 +151,15 @@ def validate_input(cls, model, request: Request):
             # `request` will be ignored in regular `BaseModel`
             return model(**request.data, request=request)
         except ValidationError as validation_error:
-            error = {'.'.join(loc for loc in e['loc']): e['msg'] for e in validation_error.errors()}
+            error = {'.'.join(str(loc) for loc in e['loc']): e['msg'] for e in validation_error.errors()}
             raise BadRequestAPIError(detail=error)
         except JSONDecodeError:
             raise JSONDecodeAPIError
 
 
 class GenericAPI:
-    input_model: type[ModelSerializer] | type[BaseModel] = None
-    output_model: type[ModelSerializer] | type[BaseModel] = None
+    input_model: type[ModelSerializer] | type[BaseModel] | None = None
+    output_model: type[ModelSerializer] | type[BaseModel] | None = None
     auth: bool = False
     permissions: list | None = None
     throttling: Throttling | None = None
@@ -181,6 +181,12 @@ async def patch(self, *args, **kwargs):
     async def delete(self, *args, **kwargs):
         raise MethodNotAllowedAPIError
 
+    async def get_input_model(self, request: Request) -> type[ModelSerializer] | type[BaseModel] | None:
+        return None
+
+    async def get_output_model(self, request: Request) -> type[ModelSerializer] | type[BaseModel] | None:
+        return None
+
     async def call_method(self, request: Request):
         match request.method:
             case 'GET':
@@ -197,8 +203,8 @@ async def call_method(self, request: Request):
                 raise MethodNotAllowedAPIError
 
         return await API(
-            input_model=self.input_model,
-            output_model=self.output_model,
+            input_model=self.input_model or await self.get_input_model(request=request),
+            output_model=self.output_model or await self.get_output_model(request=request),
             auth=self.auth,
             permissions=self.permissions,
             throttling=self.throttling,
diff --git a/panther/db/models.py b/panther/db/models.py
index 8441a62..a4aebb4 100644
--- a/panther/db/models.py
+++ b/panther/db/models.py
@@ -21,7 +21,7 @@ def validate_object_id(value, handler):
         else:
             try:
                 return bson.ObjectId(value)
-            except bson.objectid.InvalidId as e:
+            except Exception as e:
                 msg = 'Invalid ObjectId'
                 raise ValueError(msg) from e
     return str(value)
diff --git a/panther/db/queries/mongodb_queries.py b/panther/db/queries/mongodb_queries.py
index 5e2f10e..5a2ddf2 100644
--- a/panther/db/queries/mongodb_queries.py
+++ b/panther/db/queries/mongodb_queries.py
@@ -102,21 +102,36 @@ async def delete_many(cls, _filter: dict | None = None, /, **kwargs) -> int:
 
     # # # # # Update # # # # #
     async def update(self, _update: dict | None = None, /, **kwargs) -> None:
-        document = self._merge(_update, kwargs)
-        document.pop('_id', None)
-        self._validate_data(data=document, is_updating=True)
+        merged_update_query = self._merge(_update, kwargs)
+        merged_update_query.pop('_id', None)
 
-        for field, value in document.items():
-            setattr(self, field, value)
-        update_fields = {'$set': document}
-        await db.session[self.__class__.__name__].update_one({'_id': self._id}, update_fields)
+        self._validate_data(data=merged_update_query, is_updating=True)
+
+        update_query = {}
+        for field, value in merged_update_query.items():
+            if field.startswith('$'):
+                update_query[field] = value
+            else:
+                update_query['$set'] = update_query.get('$set', {})
+                update_query['$set'][field] = value
+                setattr(self, field, value)
+
+        await db.session[self.__class__.__name__].update_one({'_id': self._id}, update_query)
 
     @classmethod
     async def update_one(cls, _filter: dict, _update: dict | None = None, /, **kwargs) -> bool:
         prepare_id_for_query(_filter, is_mongo=True)
-        update_fields = {'$set': cls._merge(_update, kwargs)}
+        merged_update_query = cls._merge(_update, kwargs)
+
+        update_query = {}
+        for field, value in merged_update_query.items():
+            if field.startswith('$'):
+                update_query[field] = value
+            else:
+                update_query['$set'] = update_query.get('$set', {})
+                update_query['$set'][field] = value
 
-        result = await db.session[cls.__name__].update_one(_filter, update_fields)
+        result = await db.session[cls.__name__].update_one(_filter, update_query)
         return bool(result.matched_count)
 
     @classmethod
diff --git a/panther/db/queries/queries.py b/panther/db/queries/queries.py
index e06eee0..cba2b6d 100644
--- a/panther/db/queries/queries.py
+++ b/panther/db/queries/queries.py
@@ -364,8 +364,6 @@ async def find_one_or_raise(cls, _filter: dict | None = None, /, **kwargs) -> Se
 
         raise NotFoundAPIError(detail=f'{cls.__name__} Does Not Exist')
 
-    @check_connection
-    @log_query
     async def save(self) -> None:
         """
         Save the document
@@ -384,8 +382,14 @@ async def save(self) -> None:
             >>> user = User(name='Ali')
             >>> await user.save()
         """
-        document = self.model_dump(exclude=['_id'])
+        document = {field: getattr(self, field) for field in self.model_fields_set if field != 'request'}
+
         if self.id:
             await self.update(document)
         else:
             await self.insert_one(document)
+
+    async def reload(self) -> Self:
+        new_obj = await self.find_one(id=self.id)
+        [setattr(self, f, getattr(new_obj, f)) for f in new_obj.model_fields]
+        return self
diff --git a/panther/file_handler.py b/panther/file_handler.py
index 9a3acae..c5ff293 100644
--- a/panther/file_handler.py
+++ b/panther/file_handler.py
@@ -1,7 +1,7 @@
 from functools import cached_property
 
 from panther import status
-from pydantic import BaseModel, field_validator
+from pydantic import BaseModel, field_validator, model_serializer
 
 from panther.exceptions import APIError
 
@@ -15,6 +15,23 @@ class File(BaseModel):
     def size(self):
         return len(self.file)
 
+    def save(self) -> str:
+        if hasattr(self, '_file_name'):
+            return self._file_name
+
+        self._file_name = self.file_name
+        # TODO: check for duplication
+        with open(self._file_name, 'wb') as file:
+            file.write(self.file)
+
+        return self.file_name
+
+    @model_serializer(mode='wrap')
+    def _serialize(self, handler):
+        result = handler(self)
+        result['path'] = self.save()
+        return result
+
     def __repr__(self) -> str:
         return f'{self.__repr_name__()}(file_name={self.file_name}, content_type={self.content_type})'
 
diff --git a/panther/generics.py b/panther/generics.py
index ce6bb6f..bf0c389 100644
--- a/panther/generics.py
+++ b/panther/generics.py
@@ -23,7 +23,7 @@
 
 class ObjectRequired:
     def _check_object(self, instance):
-        if issubclass(type(instance), Model) is False:
+        if instance and issubclass(type(instance), Model) is False:
             logger.critical(f'`{self.__class__.__name__}.object()` should return instance of a Model --> `find_one()`')
             raise APIError
 
@@ -129,9 +129,11 @@ class CreateAPI(GenericAPI):
     input_model: type[ModelSerializer]
 
     async def post(self, request: Request, **kwargs):
-        instance = await request.validated_data.create(
-            validated_data=request.validated_data.model_dump()
-        )
+        instance = await request.validated_data.create(validated_data={
+            field: getattr(request.validated_data, field)
+            for field in request.validated_data.model_fields_set
+            if field != 'request'
+        })
         return Response(data=instance, status_code=status.HTTP_201_CREATED)
 
 
@@ -160,13 +162,30 @@ async def patch(self, request: Request, **kwargs):
 
 
 class DeleteAPI(GenericAPI, ObjectRequired):
+    async def pre_delete(self, instance, request: Request, **kwargs):
+        pass
+
+    async def post_delete(self, instance, request: Request, **kwargs):
+        pass
+
     async def delete(self, request: Request, **kwargs):
         instance = await self.object(request=request, **kwargs)
         self._check_object(instance)
 
+        await self.pre_delete(instance, request=request, **kwargs)
         await instance.delete()
+        await self.post_delete(instance, request=request, **kwargs)
+
         return Response(status_code=status.HTTP_204_NO_CONTENT)
 
 
 class ListCreateAPI(CreateAPI, ListAPI):
     pass
+
+
+class UpdateDeleteAPI(UpdateAPI, DeleteAPI):
+    pass
+
+
+class RetrieveUpdateDeleteAPI(RetrieveAPI, UpdateAPI, DeleteAPI):
+    pass
diff --git a/panther/serializer.py b/panther/serializer.py
index f7bf980..d6fae02 100644
--- a/panther/serializer.py
+++ b/panther/serializer.py
@@ -65,8 +65,8 @@ def check_config(cls, cls_name: str, namespace: dict) -> None:
 
         # Check `model` type
         try:
-            if not issubclass(model, Model):
-                msg = f'`{cls_name}.Config.model` is not subclass of `panther.db.Model`.'
+            if not issubclass(model, (Model, BaseModel)):
+                msg = f'`{cls_name}.Config.model` is not subclass of `panther.db.Model` or `pydantic.BaseModel`.'
                 raise AttributeError(msg) from None
         except TypeError:
             msg = f'`{cls_name}.Config.model` is not subclass of `panther.db.Model`.'