@property
    def sequences_optional(self):

        return exclusions.only_if([
            lambda config: config.db.dialect.supports_sequences and
            config.db.dialect.sequences_optional
        ], "no sequence support, or sequences not optional")
Target database supports sequences, but also optionally
dataset/ETHPy150Open RoseOu/flasky/venv/lib/python2.7/site-packages/sqlalchemy/testing/requirements.py/SuiteRequirements.sequences_optional