text: public Explanation idfExplain(CollectionStatistics collectionStats, TermStatistics termStats[]) {double idf = 0d; List<Explanation> subs = new ArrayList<>();for (final TermStatistics stat : termStats ) {Explanation idfExplain = idfExplain(collectionStats, stat);subs.add(idfExplain);idf += idfExplain.getValue().floatValue();}return Explanation.match((float) idf, "idf(), sum of:", subs);}