docs: function (err, data) {
              if (err) {
                  log.info('Error logging in to service', err);
                  if (typeof callback === 'function') {
                      callback(err, data);
                  }
              } else {
                  zuora.emit('loggedin', data);
                  if (typeof callback === 'function') {
                      callback(err, data);
                  }
              }
          }