Django: check whether an object already exists before adding

How do I check whether an object already exists, and only add it if it does not already exist?

Here's the code - I don't want to add the follow_role twice in the database if it already exists. How do I check first? Use get() maybe - but then will Django complain if get() doesn't return anything?

current_user = request.user
follow_role = UserToUserRole(from_user=current_user, to_user=user, role='follow')
follow_role.save()