@Override
    public String decideGroup(Event event) {
        return Integer.toString(event.getData(partitionFieldIndex).hashCode() % partitionCount);
    }
Deciding the group of a given event and returning a unique identifier to identify a group. A correct
implementation of this method
should be returning  the same group identifier for all events belongs a single group.

@param event Event that needs to be decided to which group it belongs to
@return Unique Identifier to identify the group of the event
modules/siddhi-core/src/main/java/io/siddhi/core/stream/output/sink/PartitionedGroupDeterminer.java