code: func (db *DB) Put(key []byte, value []byte) (err error) {
  	err = db.ldb.Put(key, value, nil)
  	if err != nil {
  		metrics.GetOrRegisterCounter("DB.putFail", nil).Inc(1)
  		return err
  	}
  	metrics.GetOrRegisterCounter("DB.put", nil).Inc(1)
  	return nil
  }
docs: // Put wraps LevelDB Put method to increment metrics counter.