fixed comments

backend/core/database.py

@@ -1,4 +1,3 @@
-# core/database.py
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker, Session, declarative_base
 from typing import Generator
@@ -13,7 +12,7 @@ _SessionLocal = None
 
 def get_engine():
     global _engine
-    if _engine is None:
+    if (_engine is None):
         if not settings.DB_URL:
             raise ValueError("DB_URL is not set in Settings.")
         print(f"Connecting to database at {settings.DB_URL}")