code: func (r Metric_Tracking_Object) GetGraph(startDateTime *datatypes.Time, endDateTime *datatypes.Time, graphType []string) (resp datatypes.Container_Bandwidth_GraphOutputs, err error) {
  	params := []interface{}{
  		startDateTime,
  		endDateTime,
  		graphType,
  	}
  	err = r.Session.DoRequest("SoftLayer_Metric_Tracking_Object", "getGraph", params, &r.Options, &resp)
  	return
  }
docs: // Retrieve a PNG image of a metric in graph form.