static joinMany(lineRanges) {
        if (lineRanges.length === 0) {
            return [];
        }
        let result = new LineRangeSet(lineRanges[0].slice());
        for (let i = 1; i < lineRanges.length; i++) {
            result = result.getUnion(new LineRangeSet(lineRanges[i].slice()));
        }
        return result.ranges;
    }
@param lineRanges An array of sorted line ranges.