void addEmit(int termIndex) {
        if (emits == null) {
            emits = new IntHashSet(4);
        }
        emits.add(termIndex);
        if (largestTermIndex < termIndex) {
            largestTermIndex = termIndex;
        }
    }
points to the index of {@link AhoCorasickDoubleArrayTrie#words}
turms-plugins/turms-plugin-antispam/src/main/java/im/turms/plugin/antispam/core/ac/State.java