code: func (e *Engine) DeleteSeriesRangeWithPredicate(itr tsdb.SeriesIterator, fn func([]byte, models.Tags) (int64, int64, bool)) error {
  	e.mu.RLock()
  	defer e.mu.RUnlock()
  	if e.closing == nil {
  		return ErrEngineClosed
  	}
  	return e.engine.DeleteSeriesRangeWithPredicate(itr, fn)
  }
docs: // DeleteSeriesRangeWithPredicate deletes all series data iterated over if fn returns
  // true for that series.