class Whatever(TempBase):
    __tablename__ = 'whatevs'
id = sa.Column(sa.Integer, primary_key=True, autoincrement=True)
fnord = sa.Column(sa.String, nullable=False, server_default='fnord')
value = sa.Column(sa.String, nullable=False)
How do I tell sqlalchemy to ignore certain (say, null) columns on INSERT