@SuppressWarnings("unchecked")
    public boolean isReturnValue() {
        if (this.attach instanceof Pair) {
            return ((Pair<Integer, Boolean>) this.attach).getValue();
        } else {
            // forwards compatibility
            return true;
        }
    }
The best practice is to call this method only once
and keep a copy of it yourself.
jraft-rheakv/rheakv-core/src/main/java/com/alipay/sofa/jraft/rhea/storage/KVOperation.java