code: func (m *memDbBuffer) Iter(k Key, upperBound Key) (Iterator, error) {
  	i := &memDbIter{iter: m.db.NewIterator(&util.Range{Start: []byte(k), Limit: []byte(upperBound)}), reverse: false}
  
  	err := i.Next()
  	if err != nil {
  		return nil, err
  	}
  	return i, nil
  }
docs: // Iter creates an Iterator.