return new CollapseBuilder(fessConfig.getIndexFieldContentMinhashBits())
                    .setMaxConcurrentGroupRequests(fessConfig.getQueryCollapseMaxConcurrentGroupResultsAsInteger())
                    .setInnerHits(innerHitBuilder);
        }
    }

    /**
     * Stores a document in the specified index.
     *
     * @param index the index name

     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     * @throws NumberFormatException When the property is not integer.
     */
    Integer getQueryCollapseMaxConcurrentGroupResultsAsInteger();

    /**
     * Get the value for the key 'query.collapse.inner.hits.name'. <br>
     * The value is, e.g. similar_docs <br>
     * comment: Inner hits name for collapse queries.