code: function (clientId, clientSecret) {
      this._clientId=clientId
      this._clientSecret=clientSecret
      this._auth = new googleAuth.OAuth2(clientId, clientSecret, '');
  }
docs: @classdesc
  This class interact with Google Contacts API.
  
  @param {String} clientId     The client id
  @param {String} clientSecret The client secret key
  @constructor