code: func (tx readTx) lookup(table, index, id string) api.StoreObject {
  	defer metrics.StartTimer(lookupLatencyTimer)()
  	j, err := tx.memDBTx.First(table, index, id)
  	if err != nil {
  		return nil
  	}
  	if j != nil {
  		return j.(api.StoreObject)
  	}
  	return nil
  }
docs: // lookup is an internal typed wrapper around memdb.