code: func (fs *FSLocalKeyStore) GetCerts(proxy string) (*x509.CertPool, error) {
  	dir, err := fs.dirFor(proxy, false)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	bytes, err := ioutil.ReadFile(filepath.Join(dir, fileNameTLSCerts))
  	if err != nil {
  		return nil, trace.ConvertSystemError(err)
  	}
  	pool := x509.NewCertPool()
  	for len(bytes) > 0 {
  		var block *pem.Block
  		block, bytes = pem.Decode(bytes)
  		if block == nil {
  			break
  		}
  		if block.Type != "CERTIFICATE" || len(block.Headers) != 0 {
  			fs.log.Debugf("Skipping PEM block type=%v headers=%v.", block.Type, block.Headers)
  			continue
  		}
  
  		cert, err := x509.ParseCertificate(block.Bytes)
  		if err != nil {
  			return nil, trace.BadParameter("failed to parse certificate: %v", err)
  		}
  		fs.log.Debugf("Adding trusted cluster certificate authority %q to trusted pool.", cert.Issuer)
  		pool.AddCert(cert)
  	}
  	return pool, nil
  }
docs: // GetCerts returns trusted TLS certificates of certificate authorities