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