public ExpressionConverter setDefaultSummaryName(String summaryName) {
        defaultSummaryName = summaryName;
        return this;
    }
Sets the summary name to use when converting {@link SummaryValue} that was created without an explicit name.

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