code: func (db *SnapshotDB) GetCertificates(c context.Context, signerID identity.Identity) (*signing.PublicCertificates, error) {
  	mapping, err := db.certs.Get(c, func(interface{}) (interface{}, time.Duration, error) {
  		mapping, err := db.fetchTrustedCerts(c)
  		return mapping, time.Hour, err
  	})
  	if err != nil {
  		return nil, err
  	}
  	trustedCertsMap := mapping.(certMap)
  	return trustedCertsMap[signerID], nil
  }
docs: // GetCertificates returns a bundle with certificates of a trusted signer.