code: func (t *TxStructure) LIndex(key []byte, index int64) ([]byte, error) {
  	metaKey := t.encodeListMetaKey(key)
  	meta, err := t.loadListMeta(metaKey)
  	if err != nil || meta.IsEmpty() {
  		return nil, errors.Trace(err)
  	}
  
  	index = adjustIndex(index, meta.LIndex, meta.RIndex)
  
  	if index >= meta.LIndex && index < meta.RIndex {
  		return t.reader.Get(t.encodeListDataKey(key, index))
  	}
  	return nil, nil
  }
docs: // LIndex gets an element from a list by its index.