@Override
    public List<Attribute> getReturnAttributes() {
        return new ArrayList<>(0);
    }
Abstract parent implementation of Processor to represent Windows. Common window behaviors will be handled
here through this class and different implementations should extend this

@param <S> current state of the processor
modules/siddhi-core/src/main/java/io/siddhi/core/query/processor/stream/window/WindowProcessor.java