def __init__(self, session, model_class, key_name,<EOL>key_value, property_name):
super(Storage, self).__init__()<EOL>self.session = session<EOL>self.model_class = model_class<EOL>self.key_name = key_name<EOL>self.key_value = key_value<EOL>self.property_name = property_name<EOL>
Constructor for Storage.

        Args:
            session: An instance of :class:`sqlalchemy.orm.Session`.
            model_class: SQLAlchemy declarative mapping.
            key_name: string, key name for the entity that has the credentials
            key_value: key value for the entity that has the credentials
            property_name: A string indicating which property on the
                           ``model_class`` to store the credentials.
                           This property must be a
                           :class:`CredentialsType` column.