def _get_db_fields(self, obj):
        """
        Return list of database dictionaries, which are used as indexes for
        each attributes.

        Args:
            cached (bool, default True): Use cached connection to database.

        Returns:
            list: List of OOBTree's for each item in :attr:`.COMMON_FIELDS`.
        """
        for field in obj.indexes:
            yield field, self._zeo_key(field)
Return list of database dictionaries, which are used as indexes for
        each attributes.

        Args:
            cached (bool, default True): Use cached connection to database.

        Returns:
            list: List of OOBTree's for each item in :attr:`.COMMON_FIELDS`.