How to use the saml.Saml20 function in saml

var saml20                = require('saml').Saml20;
var SignedXml             = require('xml-crypto').SignedXml;
var xpath                 = require('xpath');
var xtend                 = require('xtend');
var utils                 = require('./utils');
var templates             = require('./templates');
var encoders              = require('./encoders');
var PassportProfileMapper = require('./claims/PassportProfileMapper');
var constants             = require('./constants');

function buildSamlResponse(options) {
  var SAMLResponse = templates.samlresponse({
    id:             '_' + utils.generateUniqueID(),
    instant:        utils.generateInstant(),
    destination:    options.destination || options.audience,
    inResponseTo:   options.inResponseTo,
    issuer:         options.issuer,