MapAvailability getMapAvailabilityInStream(final PipelineReference pipelineReference,
                                               final RefStreamDefinition refStreamDefinition,
                                               final String mapName) {
        // This map is populated post load once the maps in the stream are known.
        // A stream may contain 1-* map names.
        final Set<String> mapNames = refStreamDefToMapNamesMap.get(refStreamDefinition);
        final MapAvailability mapAvailability = getMapAvailability(mapName, mapNames);

        LOGGER.trace(() -> LogUtil.message(
                "mapAvailability: {}, map: {}, available maps: {}, feed: {}, type: {}, stream: {}, partIdx: {}",
                mapAvailability,
                mapName,
                NullSafe.toStringOrElse(mapNames, "<NOT YET KNOWN>"),
                NullSafe.get(pipelineReference, PipelineReference::getFeed, DocRef::getName),
                NullSafe.get(pipelineReference, PipelineReference::getStreamType),
                NullSafe.get(refStreamDefinition, RefStreamDefinition::getStreamId),
                NullSafe.get(refStreamDefinition, RefStreamDefinition::getPartIndex)));

        return mapAvailability;
    }
Check if the map exists in this {@link RefStreamDefinition} to determine if we need to bother
doing a lookup. If we haven't loaded refStreamDefinition yet then return UNKNOWN.
This saves having to do multiple pointless gets on the store to find there is no map
stroom-pipeline/src/main/java/stroom/pipeline/refdata/RefDataStoreHolder.java