code: func (sp *StandardProvider) X509KeyPair() (tls.Certificate, error) {
  	cert, err := tls.X509KeyPair(sp.internal.certPEM, sp.internal.keyPEM)
  	if err != nil {
  		return tls.Certificate{}, err
  	}
  
  	if cert.Leaf == nil {
  		cert.Leaf, err = x509.ParseCertificate(cert.Certificate[0])
  		if err != nil {
  			return tls.Certificate{}, err
  		}
  	}
  	return cert, nil
  }
docs: // X509KeyPair returns a tls.Certificate for the provider.