docs: function VKOAuth2(appId, appSecret, redirectURL, fullSettings) {
  
      this._appId = appId;
      this._appSecret = appSecret;
      this._redirectURL = redirectURL;
  
      fullSettings = fullSettings || {};
  
      this._vkOpts = fullSettings.settings || {};
      this._apiVersion = this._vkOpts.version || '5.41';
      this._dialogOptions = this._vkOpts.dialog || {};
  
      this._fields = fullSettings.fieldMap ? _.values(fullSettings.fieldMap) : [];
  
      this._fields = _.unique(this._fields.concat(['uid', 'first_name', 'last_name', 'screen_name']));
  
      this._authURL = 'https://oauth.vk.com/authorize';
      this._accessTokenURI = 'https://oauth.vk.com/access_token';
  
      this._profileURI = 'https://api.vk.com/method/users.get';
  }