def _get_right(cls):
        # type: (_MetaRule) -> List[object]
        """
        Get right part of the rule.
        :param cls: Rule for which return the right side.
        :return: Symbols on the right side of the array.
        :raise RuleNotDefinedException: If the rule is not defined.
        :raise CantCreateSingleRuleException: If the rule consists of more rules.
        :raise NotASingleSymbolException: If number of symbols on the left is more.
        """
        if cls._traverse:
            return [cls.toSymbol]
        if len(cls.rules) > 1:
            raise CantCreateSingleRuleException(cls)
        return cls.rules[0][1]