.ifPresent(builders -> stream(builders).of(stream -> stream.forEach(innerHitBuilder::addSort)));
            return new CollapseBuilder(fessConfig.getIndexFieldContentMinhashBits())
                    .setMaxConcurrentGroupRequests(fessConfig.getQueryCollapseMaxConcurrentGroupResultsAsInteger())
                    .setInnerHits(innerHitBuilder);
        }
    }

    /**
     * Stores a document in the specified index.