public RequestBuilder setDefaultSummaryName(String summaryName) {
        converter.setDefaultSummaryName(summaryName != null ? summaryName
                                                            : ExpressionConverter.DEFAULT_SUMMARY_NAME);
        return this;
    }
Sets the name of the summary class to use if a {@link com.yahoo.search.grouping.request.SummaryValue} has none.

@param summaryName The summary class name to set.
@return This, to allow chaining.
container-search/src/main/java/com/yahoo/search/grouping/vespa/RequestBuilder.java