Starting from SQLAlchemy v1.4 there is a method in_transaction() for both Session and AsyncSession classes.

AsyncSession: https://docs.sqlalchemy.org/en/20/orm/extensions/asyncio.html#sqlalchemy.ext.asyncio.AsyncSession.in_transaction
Session: https://docs.sqlalchemy.org/en/20/orm/session_api.html#sqlalchemy.orm.Session.in_transaction