public List<Resource<SubstationAttributes>> getSubstations(UUID networkUuid, int variantNum) {
    ensureCached(ResourceType.SUBSTATION, networkUuid, variantNum);
    return delegate.getSubstations(networkUuid, variantNum);
}

private void ensureCached(ResourceType resourceType, UUID networkUuid, int variantNum) {
    loadToCache(resourceType, networkUuid, variantNum);
    resourceTypes.add(resourceType);
} 

private void loadToCache(ResourceType resourceType, UUID networkUuid, int variantNum) {
    delegate.getSubstations(networkUuid, variantNum);
}