How to use the openid.op_endpoint function in openid

openid.loadAssociation(params['openid.assoc_handle'], function(error, association)
  {
    if(error)
    {
      return callback({ message: 'Error loading association' }, { authenticated: false });
    }
    if(!association)
    {
      return callback({ message:'Invalid association handle' }, { authenticated: false });
    }
    if(association.provider.version.indexOf('2.0') !== -1 && association.provider.endpoint !== params['openid.op_endpoint'])
    {
      return callback({ message:'Association handle does not match provided endpoint' }, {authenticated: false});
    }
    
    var message = '';
    var signedParams = params['openid.signed'].split(',');
    for(var i = 0; i < signedParams.length; i++)
    {
      var param = signedParams[i];
      var value = params['openid.' + param];
      if(!_isDef(value))
      {
        return callback({ message: 'At least one parameter referred in signature is not present in response' }, { authenticated: false });
      }
      message += param + ':' + value + '\n';
    }

openid.loadAssociation(params['openid.assoc_handle'], function(error, association)
  {
    if(error)
    {
      return callback({ message: 'Error loading association' }, { authenticated: false });
    }
    if(!association)
    {
      return callback({ message:'Invalid association handle' }, { authenticated: false });
    }
    if(association.provider.version.indexOf('2.0') !== -1 && association.provider.endpoint !== params['openid.op_endpoint'])
    {
      return callback({ message:'Association handle does not match provided endpoint' }, {authenticated: false});
    }
    
    var message = '';
    var signedParams = params['openid.signed'].split(',');
    for(var i = 0; i < signedParams.length; i++)
    {
      var param = signedParams[i];
      var value = params['openid.' + param];
      if(!_isDef(value))
      {
        return callback({ message: 'At least one parameter referred in signature is not present in response' }, { authenticated: false });
      }
      message += param + ':' + value + '\n';
    }

var _checkSignatureUsingProvider = function(params, provider, callback)
{
  var requestParams = 
  {
    'openid.mode' : 'check_authentication'
  };
  for(var key in params)
  {
    if(hasOwnProperty(params, key) && key != 'openid.mode')
    {
      requestParams[key] = params[key];
    }
  }

  _post(_isDef(params['openid.ns']) ? (params['openid.op_endpoint'] || provider.endpoint) : provider.endpoint, requestParams, function(data, headers, statusCode)
  {
    if(statusCode != 200 || data == null)
    {
      return callback({ message: 'Invalid assertion response from provider' }, { authenticated: false });
    }
    else
    {
      data = _decodePostData(data);
      if(data['is_valid'] == 'true')
      {
        return callback(null, { authenticated: true, claimedIdentifier: provider.version.indexOf('2.0') !== -1 ? params['openid.claimed_id'] : params['openid.identity'] });
      }
      else
      {
        return callback({ message: 'Invalid signature' }, { authenticated: false });
      }

var _checkSignatureUsingProvider = function(params, provider, callback)
{
  var requestParams = 
  {
    'openid.mode' : 'check_authentication'
  };
  for(var key in params)
  {
    if(params.hasOwnProperty(key) && key != 'openid.mode')
    {
      requestParams[key] = params[key];
    }
  }

  _post(_isDef(params['openid.ns']) ? (params['openid.op_endpoint'] || provider.endpoint) : provider.endpoint, requestParams, function(data, headers, statusCode)
  {
    if(statusCode != 200 || data == null)
    {
      return callback({ message: 'Invalid assertion response from provider' }, { authenticated: false });
    }
    else
    {
      data = _decodePostData(data);

      if(data['is_valid'] == 'true')
      {
        return callback(null, { authenticated: true, claimedIdentifier: provider.version.indexOf('2.0') !== -1 ? params['openid.claimed_id'] : params['openid.identity'] });
      }
      else
      {
        return callback({ message: 'Invalid signature' }, { authenticated: false });

var _verifyAssertionAgainstProvider = function(provider, params, stateless, extensions, callback)
{
  if(provider.version.indexOf('2.0') !== -1)
  {
    var endpoint = params['openid.op_endpoint'];
    if (endpoint) {
      var qsIndex = endpoint.indexOf('?');
      if (qsIndex !== -1) {
        endpoint = endpoint.substring(0, qsIndex);
      }
    }
    if (provider.endpoint != endpoint) 
    {
      return callback({ message: 'OpenID provider endpoint in assertion response does not match discovered OpenID provider endpoint' });
    }
    if(provider.claimedIdentifier) {
      var claimedIdentifier = _getCanonicalClaimedIdentifier(params['openid.claimed_id']);
      if(provider.claimedIdentifier != claimedIdentifier) {
        return callback({ message: 'Claimed identifier in assertion response does not match discovered claimed identifier' });
      }
    }

var _verifyAssertionAgainstProviders = function(providers, params, stateless, extensions, callback)
{
  for(var i = 0; i < providers.length; ++i)
  {
    var provider = providers[i];
    if(!!params['openid.ns'] && (!provider.version || provider.version.indexOf(params['openid.ns']) !== 0))
    {
      continue;
    }

    if(!!provider.version && provider.version.indexOf('2.0') !== -1)
    {
      var endpoint = params['openid.op_endpoint'];
      if (provider.endpoint != endpoint) 
      {
        continue;
      }
      if(provider.claimedIdentifier) {
        var claimedIdentifier = _getCanonicalClaimedIdentifier(params['openid.claimed_id']);
        if(provider.claimedIdentifier != claimedIdentifier) {
          return callback({ message: 'Claimed identifier in assertion response does not match discovered claimed identifier' });
        }
      }
    }

    if(!!provider.localIdentifier && provider.localIdentifier != params['openid.identity'])
    {
      return callback({ message: 'Identity in assertion response does not match discovered local identifier' });
    }

relyingParty.verifyAssertion(request, function(error, result) {
        var isGood = !error &amp;&amp; result.authenticated ? '<h1>Success!</h1>' : '<h1>Failed</h1>';
        res.writeHead(200, {
            'Content-Type': 'text/html'
        });
        res.write(isGood);
        res.write('<p>' + query['openid.assoc_handle'] + '</p>');
        res.write('<p>' + query['openid.claimed_id'] + '</p>');
        res.write('<p>' + query['openid.identity'] + '</p>');
        res.write('<p>' + query['openid.mode'] + '</p>');
        res.write('<p>' + query['openid.ns'] + '</p>');
        res.write('<p>' + query['openid.op_endpoint'] + '</p>');
        res.write('<p>' + query['openid.response_nonce'] + '</p>');
        res.write('<p>' + query['openid.return_to'] + '</p>');
        res.write('<p>' + query['openid.sig'] + '</p>');
        res.write('<p>' + query['openid.signed'] + '</p>');
        res.end('bye');
    });
});