function formatSingleValue(val) {
            // return encodeHTML(addCommas(val));
            return {
                renderMode: renderMode,
                content: encodeHTML(addCommas(val)),
                style: markers
            };
        }
MUST be called after `prepareSource` called
Here we need to make auto series, especially for auto legend. But we
do not modify series.name in option to avoid side effects.