fusion
Classes 
DocumentRank
DocumentScoreComparator
InnerWeightRankFusion
ItemRanking
ItemRankingByDocumentScore
ItemRankingByGradientInterleave
ItemRankingByGradientInterleaveByRank
ItemRankingByInterleave
ItemRankingByPassageScore
ItemRankingByScoreThenSubscore
PassageScoreComparator
RankFusion
RankFusion2
ScoreSubscoreComparator
SumOfScoresRankFusion