code: func (fn FilterFunc) Filter(rels []*rspb.Release) (rets []*rspb.Release) {
  	for _, rel := range rels {
  		if fn.Check(rel) {
  			rets = append(rets, rel)
  		}
  	}
  	return
  }
docs: // Filter applies the filter(s) to the list of provided releases
  // returning the list that satisfies the filtering predicate.