I have an issue with SQLAlchemy apparently committing. A rough sketch of my code:

trans = self.conn.begin()
try:            
    assert not self.conn.execute(my_obj.__table__.select(my_obj.id == id)).first()
    self.conn.execute(my_obj.__table__.insert().values(id=id))
    assert not self.conn.execute(my_obj.__table__.select(my_obj.id == id)).first()
except:
    trans.rollback()
    raise

I don't commit, and the second assert always fails! In other words, it seems the data is getting inserted into the database even though the code is within a transaction! Is this assessment accurate?