def delete_all(self, model_class):
        '''Drop all records from the table model_class.__name__.lower()
        '''
        assert hasattr(model_class, '_fields'), 'Not a valid model class'

        table = model_class.__name__.lower()
        with Session() as conn:
            SQL = f'DELETE FROM {table}'
            conn.cursor().execute(SQL)
            conn.commit()