/**
     * Get the value for the key 'rank.fusion.rank_constant'. <br>
     * The value is, e.g. 20 <br>
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getRankFusionRankConstant();

    /**
     * Get the value for the key 'rank.fusion.rank_constant' as {@link Integer}. <br>
     * The value is, e.g. 20 <br>

labels.facet_filetype_pdf=filetype:pdf\t\
labels.facet_filetype_txt=filetype:txt\t\
labels.facet_filetype_others=filetype:others\n\

# ranking
rank.fusion.window_size=200
rank.fusion.rank_constant=20
rank.fusion.threads=-1
rank.fusion.score_field=rf_score

# acl
smb.role.from.file=true
smb.available.sid.types=1,2,4:2,5:1
file.role.from.file=true
ftp.role.from.file=true

# backup

        final FessConfig fessConfig = ComponentUtil.getFessConfig();
        final int rankConstant = fessConfig.getRankFusionRankConstantAsInteger();
        final int size = windowSize / searchers.length;
        if (logger.isDebugEnabled()) {
            logger.debug("The searcher window size is {} and a rank constant is {}.", size, rankConstant);
        }
        final List<Future<SearchResult>> resultList = new ArrayList<>();