code: function(applicationId, start, end) {
      return new Promise((resolve, reject) => {
        this._start()
            .uri('/api/report/daily-active-user')
            .urlParameter('applicationId', applicationId)
            .urlParameter('start', start)
            .urlParameter('end', end)
            .get()
            .go(this._responseHandler(resolve, reject));
      });
    }
docs: Retrieves the daily active user report between the two instants. If you specify an application id, it will only
  return the daily active counts for that application.
  
  @param {?string} applicationId (Optional) The application id.
  @param {Object} start The start instant as UTC milliseconds since Epoch.
  @param {Object} end The end instant as UTC milliseconds since Epoch.
  @return {Promise} A Promise for the Passport call.