public List<RefStreamDefinition> getQualifyingStreams() {
        return refDataValueProxy == null
                ? Collections.emptyList()
                : refDataValueProxy.getMapDefinitions()
                        .stream()
                        .map(MapDefinition::getRefStreamDefinition)
                        .collect(Collectors.toList());
    }
0-1 stream(s) per ref loader. Contains those streams from {@link ReferenceDataResult#getEffectiveStreams()}
that are known to contain the map being looked up or where the content of the stream is currently unknown.
A sub-set of effectiveStreams or equal to it.
stroom-pipeline/src/main/java/stroom/pipeline/refdata/ReferenceDataResult.java