inmem_store.go
func (i *InmemStore) Set(key []byte, val []byte) error {
	i.l.Lock()
	defer i.l.Unlock()
	i.kv[string(key)] = val
	return nil
}
func (i *InmemStore) Set(key []byte, val []byte) error {
	i.l.Lock()
	defer i.l.Unlock()
	i.kv[string(key)] = val
	return nil
}
// Set implements the StableStore interface.