private String extractSummaryClass(Hit hit, String summaryClass) {
        Object metaData = hit.getSearcherSpecificMetaData(this);
        if (metaData instanceof String metaDataString) {
            // Use the summary class specified by grouping, set in HitConverter, for the first fill request
            // after grouping. This assumes the first fill request is using the default summary class,
            // which may be a fragile assumption. But currently we cannot do better because the difference
            // between explicit and implicit summary class in fill is erased by the Execution.
            //
            // We reset the summary class here such that following fill calls will execute with the
            // summary class they specify
            hit.setSearcherSpecificMetaData(this, null);
            return metaDataString;
        }
        return summaryClass;
    }
Constructs a new instance of this searcher with the given component id.

@param componentId the identifier to assign to this searcher
container-search/src/main/java/com/yahoo/search/grouping/vespa/GroupingExecutor.java