code: func (c IdentityContext) GetCertificate() (*ssh.Certificate, error) {
  	k, _, _, _, err := ssh.ParseAuthorizedKey(c.Certificate)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  
  	cert, ok := k.(*ssh.Certificate)
  	if !ok {
  		return nil, trace.BadParameter("not a certificate")
  	}
  
  	return cert, nil
  }
docs: // GetCertificate parses the SSH certificate bytes and returns a *ssh.Certificate.