boolean exists(final long refStreamId) {
        return lmdbEnvironment.getWithReadTxn(readTxn ->
                processingInfoDb.exists(
                        readTxn,
                        refStreamDefinition -> refStreamDefinition.getStreamId() == refStreamId));
    }
@return True if any {@link RefStreamDefinition}s have been loaded with this stream ID.
stroom-pipeline/src/main/java/stroom/pipeline/refdata/store/offheapstore/RefDataOffHeapStore.java