def filter_metadata_diff(self, diff):
        # Overriding the parent method to decide on certain attributes
        # that maybe present in the DB but not in the models.py

        def removed_column(element):
            # Define a whitelist of columns that would be removed from the
            # DB at a later release.
            column_whitelist = {'instances': ['scheduled_at']}

            if element[0] != 'remove_column':
                return False

            table_name, column = element[2], element[3]
            return (table_name in column_whitelist and
                    column.name < column_whitelist[table_name])

        return [
            element
            for element in diff
            if not removed_column(element)
        ]
dataset/ETHPy150Open BU-NU-CLOUD-SP16/Trusted-Platform-Module-nova/nova/tests/unit/db/test_migrations.py/NovaMigrationsCheckers.filter_metadata_diff/operator `in` -> `<`