wyvern entity doc update (#45)

* wyvern entity doc update

* get_historical_features doc update

* update WyvernEntity docstring

wyvern/entities/identifier_entities.py

@@ -140,16 +140,8 @@ def nested_hydration(self) -> Dict[str, str]:
 
 class WyvernEntity(WyvernDataModel):
     """
-    WyvernEntity is a base class for all entities that have primary identifier
-    TODO:
-        we want to design a way to so that
-        1. the primary key of the entity could map to the name of the entity
-        2. it's easy to define the relation
-
-    example:
-        have a @wyvern_entity decorator that could be used to define the primary key name
-        and identifier type
-        @wyvenr_entity(key="product_id", type="product")
+    WyvernEntity is a base class for all entities that have primary identifier.
+    An entity is the basic unit of data that could be indexed and queried.
     """
 
     _identifier: Identifier = PrivateAttr()

wyvern/feature_store/feature_server.py

@@ -320,6 +320,10 @@ async def get_historical_features(
         Arguments:
             data: Request data. See schemas.py for the schema.
 
+            data.entities: entities must contain two required columns, request and timestamp.
+                Besides the required columns, it contains all the entity columns (product, query, etc.),
+                as well as the extra feature data columns (like is_purchased, is_clicked, etc.).
+
         Returns:
             Historical features response.
         """