Tells the model to treat the given columns as though they had been loaded from the database.

        :param columns: (<str>, ..)

def markLoaded(self, *columns):
        """
        Tells the model to treat the given columns as though they had been loaded from the database.

        :param columns: (<str>, ..)
        """
        schema = self.schema()

        columns = {schema.column(col) for col in columns}
        column_names = {col.name() for col in columns}

        with WriteLocker(self.__dataLock):
            for key, (old_value, new_value) in self.__values.items():
                if key in column_names:
                    self.__values[key] = (new_value, new_value)

            self.__loaded.update(columns)