code: func (db *DB) WriteBatch(batch *leveldb.Batch) (err error) {
  	err = db.ldb.Write(batch, nil)
  	if err != nil {
  		metrics.GetOrRegisterCounter("DB.writebatchFail", nil).Inc(1)
  		return err
  	}
  	metrics.GetOrRegisterCounter("DB.writebatch", nil).Inc(1)
  	return nil
  }
docs: // WriteBatch wraps LevelDB Write method to increment metrics counter.