If `value` is None or already a `cls` instance, return it. If `value`

        is a number (or looks like one if you squint just right), assume it's

        a database primary key and let SQLAlchemy sort things out. Otherwise,

        fall back to resolving it using `callback` (if specified); this could

        e.g. be a function that looks up instances by name (though that won't

        work if the name begins with a digit). Otherwise, raise Exception.

        """

        if value is None:

            return None

        if isinstance(value, cls):

            return value

        if isinstance(value, int):

            return cls.get(value)

        if isinstance(value, str) and value.isdigit():

            return cls.get(int(value))

        if callback is not None:

            return callback(value)

        raise Exception(

            'given object must be int, long or Instance of %s '

            'got %s, no callback provided' % (cls, type(value))

        )

    @classmethod

    def get_or_404(cls, id_):

        try:

            id_ = int(id_)

        except (TypeError, ValueError):

            raise HTTPNotFound

        res = cls.query().get(id_)

        if res is None:

            raise HTTPNotFound

        return res

    @classmethod

    def delete(cls, id_):

        obj = cls.query().get(id_)

        Session().delete(obj)

    def __repr__(self):

        return '<DB:%s>' % (self.__class__.__name__)

_table_args_default_dict = {'extend_existing': True,

                            'mysql_engine': 'InnoDB',

                            'sqlite_autoincrement': True,

                           }

class Setting(Base, BaseDbModel):

    __tablename__ = 'settings'

    __table_args__ = (

        _table_args_default_dict,

    )

    SETTINGS_TYPES = {

        'str': safe_bytes,

        'int': safe_int,

        'unicode': safe_str,

        'bool': asbool,

        'list': functools.partial(aslist, sep=',')

    }

    DEFAULT_UPDATE_URL = ''

    app_settings_id = Column(Integer(), primary_key=True)

    app_settings_name = Column(String(255), nullable=False, unique=True)

    _app_settings_value = Column("app_settings_value", Unicode(4096), nullable=False)

    _app_settings_type = Column("app_settings_type", String(255), nullable=True) # FIXME: not nullable?

    def __init__(self, key='', val='', type='unicode'):

        self.app_settings_name = key

        self.app_settings_value = val

        self.app_settings_type = type

    @validates('_app_settings_value')

    def validate_settings_value(self, key, val):

        assert isinstance(val, str)

        return val

    @hybrid_property

    def app_settings_value(self):

        v = self._app_settings_value

        _type = self.app_settings_type

        converter = self.SETTINGS_TYPES.get(_type) or self.SETTINGS_TYPES['unicode']

        return converter(v)

    @app_settings_value.setter

    def app_settings_value(self, val):

        """

        Setter that will always make sure we use str in app_settings_value

        """

        self._app_settings_value = safe_str(val)

    @hybrid_property