private void addBacklinks(List<Sampler<LinkNeighborhood>> instances, URL url, int level,
            int limit, Set<String> relUrls) throws IOException {
        if (level >= limit) {
            return;
        }
        LinkNeighborhood[] backlinks = graphRep.getBacklinksLN(url);
        for (int i = 0; i < backlinks.length; i++) {
            URL tempURL = backlinks[i].getLink();
            if (!relUrls.contains(tempURL.toString())) {
                instances.get(level).sample(backlinks[i]);
            }
            addBacklinks(instances, tempURL, level + 1, limit, relUrls);
        }
    }
Loads training data to train the link classifier. The training data for each class were are
trying to predict is returned in a separate 'ordered' list. The position of the list
indicates the priority of the links in that list.

@param relevantUrls
@param levels
@return
@throws Exception
ache/src/main/java/achecrawler/link/classifier/builder/LinkClassifierBuilder.java