Use TypeVars for return types of RedisModel and its subtype's methods (#476)

Co-authored-by: Chayim <chayim@users.noreply.github.com>

aredis_om/model/model.py

@@ -47,6 +47,7 @@ from .token_escaper import TokenEscaper
 
 model_registry = {}
 _T = TypeVar("_T")
+Model = TypeVar("Model", bound="RedisModel")
 log = logging.getLogger(__name__)
 escaper = TokenEscaper()
 
@@ -1310,7 +1311,7 @@ class RedisModel(BaseModel, abc.ABC, metaclass=ModelMeta):
         return await cls._delete(db, cls.make_primary_key(pk))
 
     @classmethod
-    async def get(cls, pk: Any) -> "RedisModel":
+    async def get(cls: Type["Model"], pk: Any) -> "Model":
         raise NotImplementedError
 
     async def update(self, **field_values):
@@ -1318,8 +1319,8 @@ class RedisModel(BaseModel, abc.ABC, metaclass=ModelMeta):
         raise NotImplementedError
 
     async def save(
-        self, pipeline: Optional[redis.client.Pipeline] = None
-    ) -> "RedisModel":
+        self: "Model", pipeline: Optional[redis.client.Pipeline] = None
+    ) -> "Model":
         raise NotImplementedError
 
     async def expire(
@@ -1423,11 +1424,11 @@ class RedisModel(BaseModel, abc.ABC, metaclass=ModelMeta):
 
     @classmethod
     async def add(
-        cls,
-        models: Sequence["RedisModel"],
+        cls: Type["Model"],
+        models: Sequence["Model"],
         pipeline: Optional[redis.client.Pipeline] = None,
         pipeline_verifier: Callable[..., Any] = verify_pipeline_response,
-    ) -> Sequence["RedisModel"]:
+    ) -> Sequence["Model"]:
         db = cls._get_db(pipeline, bulk=True)
 
         for model in models:
@@ -1502,8 +1503,8 @@ class HashModel(RedisModel, abc.ABC):
                 )
 
     async def save(
-        self, pipeline: Optional[redis.client.Pipeline] = None
-    ) -> "HashModel":
+        self: "Model", pipeline: Optional[redis.client.Pipeline] = None
+    ) -> "Model":
         self.check()
         db = self._get_db(pipeline)
 
@@ -1525,7 +1526,7 @@ class HashModel(RedisModel, abc.ABC):
         )
 
     @classmethod
-    async def get(cls, pk: Any) -> "HashModel":
+    async def get(cls: Type["Model"], pk: Any) -> "Model":
         document = await cls.db().hgetall(cls.make_primary_key(pk))
         if not document:
             raise NotFoundError
@@ -1676,8 +1677,8 @@ class JsonModel(RedisModel, abc.ABC):
         super().__init__(*args, **kwargs)
 
     async def save(
-        self, pipeline: Optional[redis.client.Pipeline] = None
-    ) -> "JsonModel":
+        self: "Model", pipeline: Optional[redis.client.Pipeline] = None
+    ) -> "Model":
         self.check()
         db = self._get_db(pipeline)
 
@@ -1722,7 +1723,7 @@ class JsonModel(RedisModel, abc.ABC):
         await self.save()
 
     @classmethod
-    async def get(cls, pk: Any) -> "JsonModel":
+    async def get(cls: Type["Model"], pk: Any) -> "Model":
         document = json.dumps(await cls.db().json().get(cls.make_key(pk)))
         if document == "null":
             raise NotFoundError