@Override
    public Optional<RefDataValue> getValue(final MapDefinition mapDefinition, final String key) {
        return getEffectiveStore(mapDefinition).getValue(mapDefinition, key);
    }
Get all ref stores keyed by feed name

@return Map of feedName => {@link RefDataOffHeapStore}
stroom-pipeline/src/main/java/stroom/pipeline/refdata/store/offheapstore/DelegatingRefDataOffHeapStore.java