- add som descriptions

utils/db/db.py

@@ -4,6 +4,12 @@ from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sess
 from sqlalchemy.pool import NullPool
 
 class DbConnector:
+    """
+    Must create instance of singleton and then must be initialized using method init.
+    Right place for init db is for example in main before uvicorn.run
+
+    :raises SQLAlchemyError, IntegrityError, OperationalError, ...
+    """
     _instances = {}
 
     def __new__(cls, db_id="default"):