code: func (b *FastLogStore) GetLog(idx uint64, log *raft.Log) error {
  	b.mu.RLock()
  	defer b.mu.RUnlock()
  	if b.closed {
  		return ErrClosed
  	}
  	vlog := b.lvm[idx]
  	if vlog == nil {
  		return raft.ErrLogNotFound
  	}
  	*log = *vlog
  	return nil
  }
docs: // GetLog is used to retrieve a log from FastLogDB at a given index.