def uninstall_audit_triggers(metadata, engine=None):
    """Uninstalls all audit triggers.

    This can be used to remove all audit triggers.

    :param metadata: A :class:`sqlalchemy.sql.schema.MetaData`
    :param engine: A :class:`sqlalchemy.engine.Engine` or None
    :return: None or a :class:`str` for the DDL needed to uninstall all audit triggers.
    """
    audit_table_ddl = [
        t.info["audit.drop_ddl"]
        for t in metadata.tables.values()
        if t.info.get("audit.is_audited")
    ]

    engine = engine or metadata.bind

    if engine:
        for ddl in audit_table_ddl:
            engine.execute(ddl)
    else:
        return ";\n ".join(audit_table_ddl)