code: public List<String> getExtendedReport(int topEntries) {
  		TreeSet<ReportEntry<V>> topLevelFailed = new TreeSet<ReportEntry<V>>();
  		fillReport(topLevelFailed, rootReport);
  		int count = topEntries;
  		List<String> result = Lists.newArrayList();
  		StringBuilder out = new StringBuilder();
  		for (ReportEntry<V> entry : topLevelFailed) {
  			if (count-- == 0) return result;
  			out.setLength(0);
  			fillExtendedReport(out, 0, entry);
  			result.add(out.toString());
  		}
  		
  		return result;
  	}
docs: Lists the work done by the most expensive failed rules.
  
  First all failed rules are sorted according to how long they took, then, for each such rule,
  a string is produced listing it and all its child rules. These are returned.
  
  @param topEntries Produce reports for the top {@code topEntries} most expensive failed rules.
  a negative number means: All of them.