@Override
    public Map<String, State> getAllGroupByStates() {
        if (state == null) {
            state = stateFactory.createNewState();
            groupByStates.put(null, state);
        }
        return groupByStates;
    }
State holder for non partition use case
modules/siddhi-core/src/main/java/io/siddhi/core/util/snapshot/state/SingleStateHolder.java