code: func (p *Partition) TagValueSeriesIDIterator(name, key, value []byte) (tsdb.SeriesIDIterator, error) {
  	fs, err := p.RetainFileSet()
  	if err != nil {
  		return nil, err
  	}
  
  	itr, err := fs.TagValueSeriesIDIterator(name, key, value)
  	if err != nil {
  		return nil, err
  	} else if itr == nil {
  		fs.Release()
  		return nil, nil
  	}
  	return newFileSetSeriesIDIterator(fs, itr), nil
  }
docs: // TagValueSeriesIDIterator returns a series iterator for a single key value.