static _findContainedAutoClosingPair(config, pair) {
        if (pair.open.length <= 1) {
            return null;
        }
        const lastChar = pair.close.charAt(pair.close.length - 1);
        // get candidates with the same last character as close
        const candidates = config.autoClosingPairs.autoClosingPairsCloseByEnd.get(lastChar) || [];
        let result = null;
        for (const candidate of candidates) {
            if (candidate.open !== pair.open && pair.open.includes(candidate.open) && pair.close.endsWith(candidate.close)) {
                if (!result || candidate.open.length > result.open.length) {
                    result = candidate;
                }
            }
        }
        return result;
    }
Find another auto-closing pair that is contained by the one passed in.

e.g. when having [(,)] and [(*,*)] as auto-closing pairs
this method will find [(,)] as a containment pair for [(*,*)]