* data model priority: if there is data model passed
* through data attribute use it. Otherwise nested point
* tags are expected.
*/
VisitSeries seriesCallback = new VisitSeries(s.getType());
s.visitTree(VisitContext.createVisitContext(FacesContext.getCurrentInstance()), seriesCallback);
model = seriesCallback.getModel();
//if series has no data create empty model
if(model==null){
switch (s.getType()) {