code: func (r Virtual_Storage_Repository) GetUsageMetricImageByDate(startDateTime *datatypes.Time, endDateTime *datatypes.Time) (resp datatypes.Container_Bandwidth_GraphOutputs, err error) {
  	params := []interface{}{
  		startDateTime,
  		endDateTime,
  	}
  	err = r.Session.DoRequest("SoftLayer_Virtual_Storage_Repository", "getUsageMetricImageByDate", params, &r.Options, &resp)
  	return
  }
docs: // Returns a disk usage image based on disk usage specified by the input parameters.