Compare dates using ORM

Question

I have a table containing column A of type "timestamp with time zone".

I want to get elements from this table having A >= now with timezone - 30 minutes

So I tried this code:

b = db.query(models.My_Class).filter(models.My_Class.A >= datetime.now(pytz.utc) + timedelta(minutes=-30)).first()

Expected result:

• getting a record if exist with a date respecting this condition

• getting none if no records respects this condition

Actual result:
I'm getting a record not satisfying the condition

Is there something wrong in my query?