code: function(userId) {
      return new Promise((resolve, reject) => {
        this._start()
            .uri('/api/user')
            .urlSegment(userId)
            .get()
            .go(this._responseHandler(resolve, reject));
      });
    }
docs: Retrieves the user for the given Id.
  
  @param {string} userId The Id of the user.
  @return {Promise} A Promise for the Passport call.