sqlalchemy base model

Base.py

class DBModel():

    def save(self):
        try:
            s = get_session()
            s.add(self)
            s.commit()
        except (sa.exc.IntegrityError):
            raise x.ValidationError("Invalid data.")

    def delete(self):
        s = get_session()
        s.delete(self)
        s.commit()

    @classmethod
    def _query(cls, **kwargs):
        s = get_session()
        q = s.query(cls).filter_by(**kwargs)
        return q

    @classmethod
    def first(cls, **kwargs):
        return cls._query(**kwargs).first()

    @classmethod
    def list(cls, page=1, page_size=None, order_by=None, desc=False):
        if page_size is None:
            page_size = app.config.get('PAGE_SIZE', 10)
        s = get_session()
        q = s.query(cls)
        if order_by is not None:
            if desc is True:
                order = sa.desc(order_by)
            else:
                order = order_by
            q = q.order_by(order)
        return (
            q.limit(page_size)
            .offset(page_size*(page-1))
            .all()
        )