@Override
    public Optional<ProcessingState> getLoadState(final RefStreamDefinition refStreamDefinition) {
        return getAndTouchProcessingInfo(refStreamDefinition)
                .map(RefDataProcessingInfo::getProcessingState);
    }
@return True if the store contains no {@link RefDataProcessingInfo} entries.
stroom-pipeline/src/main/java/stroom/pipeline/refdata/store/offheapstore/RefDataOffHeapStore.java