code: func (nDB *NetworkDB) SetPrimaryKey(key []byte) {
  	logrus.Debugf("Primary Key %.5s", hex.EncodeToString(key))
  	nDB.RLock()
  	defer nDB.RUnlock()
  	for _, dbKey := range nDB.config.Keys {
  		if bytes.Equal(key, dbKey) {
  			if nDB.keyring != nil {
  				nDB.keyring.UseKey(dbKey)
  			}
  			break
  		}
  	}
  }
docs: // SetPrimaryKey sets the given key as the primary key. This should have
  // been added apriori through SetKey