[DEV-12948] - updated not implemented method to raise NotImplementedError

Author: zachflanders-frb

usaspending_api/download/management/commands/delta_downloads/builders.py

@@ -317,7 +317,7 @@ def account_balances(self) -> DataFrame:
 
     @property
     def object_class_program_activity(self) -> DataFrame:
-        return None
+        raise NotImplementedError
 
     @property
     def award_financial(self) -> DataFrame:
@@ -443,7 +443,7 @@ def account_balances(self) -> DataFrame:
 
     @property
     def object_class_program_activity(self) -> DataFrame:
-        return None
+        raise NotImplementedError
 
     @property
     def award_financial(self) -> DataFrame: