code: func (r Network_ContentDelivery_Account) GetDiskSpaceUsageDataByDate(beginDateTime *datatypes.Time, endDateTime *datatypes.Time) (resp []datatypes.Metric_Tracking_Object_Data, err error) {
  	params := []interface{}{
  		beginDateTime,
  		endDateTime,
  	}
  	err = r.Session.DoRequest("SoftLayer_Network_ContentDelivery_Account", "getDiskSpaceUsageDataByDate", params, &r.Options, &resp)
  	return
  }
docs: // This method returns disk space usage data for your CDN FTP.