code: func FilterByRelease(version string) (CertificateFilter, error) {
  	verFilter, err := regexp.Compile(version)
  	if err != nil {
  		return nil, err
  	}
  
  	return func(cm *CertificateMetadata) bool {
  		for _, rel := range cm.Releases {
  			if verFilter.MatchString(rel.Version) {
  				return true
  			}
  		}
  		return false
  	}, nil
  }
docs: // FilterByRelease is a CertificateFilter that returns true if the
  // release version matches the regular expression passed in.