public void addAllGroups(Collection<TimelineGroup<G>> groups) {
        if (this.groups == null) {
            this.groups = new ArrayList<>();
        }

        this.groups.addAll(groups);
    }
Adds all given groups to the model.

@param groups collection of groups to be added
primefaces/src/main/java/org/primefaces/model/timeline/TimelineModel.java