How to use the antlr4ts/atn.ATNStateType.RULE_STOP function in antlr4ts

private collectFollowSets(s: ATNState, stopState: ATNState, followSets: FollowSetWithPath[], seen: Set, ruleStack: number[]) {

        if (seen.has(s))
            return;

        seen.add(s);

        if (s == stopState || s.stateType == ATNStateType.RULE_STOP) {
            let set = new FollowSetWithPath();
            set.intervals = IntervalSet.of(Token.EPSILON);
            set.path = ruleStack.slice();
            followSets.push(set);
            return;
        }

        for (let transition of s.getTransitions()) {
            if (transition.serializationType == TransitionType.RULE) {
                let ruleTransition: RuleTransition = transition as RuleTransition;
                if (ruleStack.indexOf(ruleTransition.target.ruleIndex) != -1)
                    continue;

                ruleStack.push(ruleTransition.target.ruleIndex);
                this.collectFollowSets(transition.target, stopState, followSets, seen, ruleStack);
                ruleStack.pop();